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12 Forensic Toxicology
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LEARNING OBJECTIVES
After studying this chapter, you should be able to:
• Explain how alcohol is absorbed into the bloodstream, transported throughout the body, and eliminated
by oxidation and excretion.
• Understand the process by which alcohol is excreted in the breath via the lungs.
• Understand the concepts of infrared and fuel cell breath-testing devices for alcohol testing.
• Describe commonly employed field sobriety tests to assess alcohol impairment.
• List and contrast laboratory procedures for measuring the concentration of alcohol in the blood.
• Relate the precautions necessary to properly preserve blood in order to analyze its alcohol content.
• Understand the significance of implied-consent laws and the Schmerber v. California case to traffic
enforcement.
• Describe techniques that forensic toxicologists use to isolate and identify drugs and poisons.
• Appreciate the significance of finding a drug in human tissues and organs as it relates to assessing
impairment.
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• Describe how to coordinate the drug recognition expert (DRE) program with a forensic toxicology
finding.
WHAT KILLED NAPOLEON?
Napoleon I, emperor of France, was sent into exile on the remote island of St. Helena by the British after his defeat at
the Battle of Waterloo in 1815. St. Helena was hot, unsanitary, and rampant with disease. There, Napoleon was
confined to a large reconstructed agricultural building known as Longwood House. Boredom and unhealthy living
conditions gradually took their toll on Napoleon’s mental and physical state. He began suffering from severe
abdominal pains and experienced swelling of the ankles and general weakness of his limbs. From the fall of 1820,
Napoleon’s health began to deteriorate rapidly until he died on May 5, 1821. An autopsy concluded the cause of death
was stomach cancer.
Because Napoleon died in British captivity, it was inevitable that numerous conspiratorial theories would develop to
account for his death. One of the most fascinating inquiries was conducted by a Swedish dentist, Sven Forshufvud,
who systematically correlated the clinical symptoms of Napoleon’s last days to those of arsenic poisoning. He
published a book in Swedish about this case in 1961 For Forshufvud, the key to unlocking the cause of Napoleon’s
death rested with Napoleon’s hair. Forshufvud arranged to have Napoleon’s hair measured for arsenic content by
neutron activation analysis and found it consistent with arsenic poisoning. Nevertheless, the cause of Napoleon’s
demise is still a matter for debate and speculation. Other Napoleon hairs collected in 1805 and 1814 have also shown
high concentrations of arsenic, giving rise to the speculation that Napoleon was innocently exposed to arsenic over a
long period of time. Even hair collected from Napoleon’s three sisters show significant levels of arsenic. Some
scientists question whether Napoleon even had the clinical symptoms associated with arsenic poisoning. In truth,
forensic science may never be able to answer the question, What killed Napoleon?
Role of Forensic Toxicology
Because the uncontrolled use of drugs has become a worldwide problem affecting all segments of society, the role of
the toxicologist has taken on new and added significance. Toxicologists detect and identify drugs and poisons in body
fluids, tissues, and organs. Their services are not only required in such legal institutions as crime laboratories and
medical examiners’ offices, but they also reach into hospital laboratories—where identifying a drug overdose may
represent the difference between life and death—and into various health facilities that monitor the intake of drugs and
other toxic substances. Primary examples include performing blood tests on children exposed to leaded paints and
analyzing the urine of addicts enrolled in methadone maintenance programs.
toxicologist An individual charged with the responsibility of detecting and identifying the presence of drugs and
poisons in body fluids, tissues, and organs.
The role of the forensic toxicologist is limited to matters that pertain to violations of criminal law. However,
responsibility for performing toxicological services in a criminal justice system varies considerably throughout the
United States. In systems with a crime laboratory independent of the medical examiner’s office, this responsibility may
reside with one or the other, or it may be shared by both. Some systems, however, take advantage of the expertise of
government health department laboratories and assign this role to them. Nevertheless, whatever facility handles this
work, its caseload will reflect the prevailing popularity of the drugs that are abused in the community. In most cases,
this means that the forensic toxicologist handles numerous requests to determine the presence of alcohol in the body.
All of the statistical and medical evidence available shows that ethyl alcohol—a legal, over-the-counter substance—is
the most heavily abused drug in Western countries. Forty percent of all traffic deaths in the United States—nearly
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17,500 fatalities per year—are alcohol related, along with more than two million injuries that require hospital
treatment each year. This highway death toll, as well as the untold damage to life, limb, and property, shows the
dangerous consequences of alcohol abuse. Because of the prevalence of alcohol in the toxicologist’s work, we will
begin by taking a closer look at how the body processes and responds to alcohol.
Quick Review
• Forensic toxicologists detect and identify drugs and poisons in body fluids, tissues, and organs in situations that
involve violations of criminal laws.
• Ethyl alcohol is the most heavily abused drug in Western countries.
Toxicology of Alcohol
The subject of the alcohol analysis immediately confronts us with the primary objective of forensic toxicology: to
detect and isolate drugs in the body so that their influence on human behavior can be determined. Knowing how the
body metabolizes alcohol provides the key to understanding its effects on human behavior. This knowledge has also
made possible the development of instruments that measure the presence and concentration of alcohol in individuals
suspected of driving while under its influence.
METABOLISM OF ALCOHOL
All chemicals that enter the body are eventually broken down by chemicals within the body and transformed into other
chemicals that are easier to eliminate. This process of transformation, called metabolism , consists of three basic steps:
absorption, distribution, and elimination.
metabolism The transformation of a chemical in the body to other chemicals for the purpose of facilitating its
elimination from the body.
ABSORPTION AND DISTRIBUTION
Alcohol, or ethyl alcohol, is a colorless liquid normally diluted with water and consumed as a beverage. Alcohol
appears in the blood within minutes after it has been consumed and slowly increases in concentration while it is being
absorbed from the stomach and the small intestine into the bloodstream. During the absorption phase, alcohol slowly
enters the body’s bloodstream and is carried to all parts of the body. When the absorption period is completed, the
alcohol becomes distributed uniformly throughout the watery portions of the body—that is, throughout about two-
thirds of the body volume. Fat, bones, and hair are low in water content and therefore contain little alcohol, whereas
alcohol concentration in the rest of the body is fairly uniform. After absorption is completed, a maximum alcohol level
is reached in the blood, and the postabsorption period begins. Then the alcohol concentration slowly decreases until it
reaches zero again.
absorption The passage of substances such as alcohol across the wall of the stomach and small intestine into the
bloodstream.
Many factors determine the rate at which alcohol is absorbed into the bloodstream, including the total time taken to
consume the drink, the alcohol content of the beverage, the amount consumed, and the quantity and type of food
present in the stomach at the time of drinking. With so many variables, it is difficult to predict just how long the
absorption process will require. For example, beer is absorbed more slowly than an equivalent concentration of alcohol
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in water, apparently because of the carbohydrates in beer. Also, alcohol consumed on an empty stomach is absorbed
faster than an equivalent amount of alcohol taken when there is food in the stomach (see Figure 12-1 ).
ELIMINATION
As the alcohol is circulated by the bloodstream, the body begins to eliminate it. Alcohol is eliminated through two
mechanisms: oxidation and excretion . Nearly all of the alcohol consumed (95 to 98 percent) is eventually oxidized to
carbon dioxide and water. Oxidation takes place almost entirely in the liver. There, in the presence of the enzyme
alcohol dehydrogenase , the alcohol is converted into acetaldehyde and then to acetic acid. The acetic acid is
subsequently oxidized in practically all parts of the body, becoming carbon dioxide and water.
oxidation The combination of oxygen with other substances to produce new products.
excretion The elimination of substances such as alcohol from the body in an unchanged state, typically in breath and
urine.
The remaining alcohol is excreted, unchanged, in the breath, urine, and perspiration. Most significant, the amount of
alcohol exhaled in the breath is in direct proportion to the concentration of alcohol in the blood. This observation has
had a tremendous impact on the technology and procedures used for blood-alcohol testing. The development of
instruments to reliably measure breath for its alcohol content has made possible the testing of millions of people in a
quick, safe, and convenient manner.
The fate of alcohol in the body is therefore relatively simple—namely, absorption into the bloodstream, distribution
throughout the body’s water, and finally, elimination by oxidation and excretion. The elimination, or “burn-off,” rate of
alcohol varies in different individuals; 0.015 percent w/v (weight per volume) per hour is the average rate after the
absorption process is complete.
1
However, this figure is an average that varies by as much as 30 percent among
individuals.
FIGURE 12-1 Blood-alcohol concentrations after ingestion of 2 ounces of
pure alcohol mixed in 8 ounces of water (equivalent to about 5 ounces of
80-proof vodka).
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Courtesy US Department of Transportation, Washington, DC
BLOOD-ALCOHOL CONCENTRATION
Logically, the most obvious measure of intoxication would be the amount of liquor a person has consumed.
Unfortunately, most arrests are made after the fact, when such information is not available to legal authorities;
furthermore, even if these data could be collected, numerous related factors, such as body weight and the rate of
alcohol’s absorption into the body, are so variable that it would be impossible to prescribe uniform standards that
would yield reliable alcohol intoxication levels for all individuals.
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Theoretically, for a true determination of the quantity of alcohol impairing an individual’s normal body functions, it
would be best to remove a portion of brain tissue and analyze it for alcohol content. For obvious reasons, this cannot
be done on living subjects. Consequently, toxicologists concentrate on the blood, which provides the medium for
circulating alcohol throughout the body, carrying it to all tissues including the brain. Fortunately, experimental
evidence supports this approach and shows blood-alcohol concentration to be directly proportional to the concentration
of alcohol in the brain. From the medicolegal point of view, blood-alcohol levels have become the accepted standard
for relating alcohol intake to its effect on the body.
The longer the total time required for complete absorption to occur, the lower the peak alcohol concentration in the
blood. Depending on a combination of factors, maximum blood-alcohol concentration may not be reached until two or
three hours have elapsed from the time of consumption. However, under normal social drinking conditions, it takes
anywhere from thirty to ninety minutes from the time of the final drink until the absorption process is completed.
As noted earlier, alcohol becomes concentrated evenly throughout the watery portions of the body. This knowledge can
be useful for the toxicologist analyzing a body for the presence of alcohol. If blood is not available, as in some
postmortem situations, a medical examiner can select a water-rich organ or fluid—for example, the brain,
cerebrospinal fluid, or vitreous humor—to test the body’s alcohol content to a reasonable degree of accuracy.
FIGURE 12-2 A simplified diagram of the human circulatory system.
Vessels shown in red contain oxygenated blood; vessels shown in gray
contain deoxygenated blood.
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ALCOHOL IN THE CIRCULATORY SYSTEM
The extent to which an individual may be under the influence of alcohol is usually determined by measuring the
quantity of alcohol present in the blood system. Normally, this is accomplished in one of two ways: (1) by analyzing
the blood for its alcohol content or (2) by measuring the alcohol content of the breath. In either case, the significance
and meaning of the results can better be understood when the movement of alcohol through the circulatory system is
studied.
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Humans, like all vertebrates, have a closed circulatory system, which consists basically of a heart and numerous
arteries, capillaries, and veins. An artery is a blood vessel carrying blood away from the heart, and a vein is a vessel
carrying blood back toward the heart. Capillaries are tiny blood vessels that connect the arteries with the veins. The
exchange of materials between the blood and the other tissues takes place across the thin walls of the capillaries. A
schematic diagram of the circulatory system is shown in Figure 12-2 .
artery A blood vessel that carries blood away from the heart.
vein A blood vessel that transports blood toward the heart.
capillary A tiny blood vessel that receives blood from arteries and carries it to veins, and across whose walls the
exchange of materials between the blood and the tissues takes place.
INGESTION AND DISTRIBUTION
Let us now trace the movement of alcohol through the human circulatory system. After alcohol is ingested, it moves
down the esophagus into the stomach. About 20 percent of the alcohol is absorbed through the stomach walls into the
portal vein of the blood system. The remaining alcohol passes into the blood through the walls of the small intestine.
Once in the blood, the alcohol is carried to the liver, where enzymes begin to break it down.
As the blood (still carrying the alcohol) leaves the liver, it moves up to the heart. The blood enters the upper right
chamber of the heart, called the right atrium (or auricle), and is forced into the lower right chamber of the heart, known
as the right ventricle. Having returned to the heart from its circulation through the tissues, the blood at this time
contains very little oxygen and much carbon dioxide. Consequently, the blood must be pumped up to the lungs,
through the pulmonary artery, to be replenished with oxygen.
AERATION
In the lungs, the respiratory system bridges with the circulatory system so that oxygen can enter the blood and carbon
dioxide can leave it. As shown in Figure 12-3 , the pulmonary artery branches into capillaries lying close to tiny pear-
shaped sacs called alveoli . The lungs contain about 250 million alveoli, all located at the ends of the bronchial tubes.
The bronchial tubes connect to the windpipe (trachea), which leads up to the mouth and nose (see Figure 12-4 ). At the
surface of the alveolar sacs, blood flowing through the capillaries comes into contact with fresh oxygenated air in the
sacs.
alveoli Small sacs in the lungs through whose walls air and other vapors are exchanged between the breath and the
blood.
FIGURE 12-3 Gas exchange in the lungs. Blood flows from the pulmonary
artery into vessels that lie close to the walls of the alveoli. Here the blood
gives up its carbon dioxide and absorbs oxygen. The oxygenated blood
leaves the lungs via the pulmonary vein and returns to the heart.
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A rapid exchange now takes place between the fresh air in the sacs and the spent air in the blood. Oxygen passes
through the walls of the alveoli into the blood while carbon dioxide is discharged from the blood into the air. If, during
this exchange, alcohol or any other volatile substance is in the blood, it too will pass into the alveoli. During breathing,
the carbon dioxide and alcohol are expelled through the nose and mouth, and the alveoli are replenished with fresh
oxygenated air breathed into the lungs, allowing the process to begin all over again.
The temperature at which the breath leaves the mouth is normally 34°C. At this temperature, the ratio of alcohol in the
blood to alcohol in alveolar air is approximately 2,100 to 1. In other words, 1 milliliter of blood contains nearly the
same amount of alcohol as 2,100 milliliters of alveolar breath.
RECIRCULATION AND ABSORPTION
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Now let’s return to the circulating blood. After emerging from the lungs, the oxygenated blood is rushed back to the
upper left chamber of the heart (left atrium) by the pulmonary vein. When the left atrium contracts, it forces the blood
through a valve into the left ventricle, which is the lower left chamber of the heart. The left ventricle then pumps the
freshly oxygenated blood into the arteries, which carry the blood to all parts of the body. Each of these arteries, in turn,
branches into smaller arteries, which eventually connect with the numerous tiny capillaries embedded in the tissues.
Here the alcohol moves out of the blood and into the tissues. The blood then runs from the capillaries into tiny veins
that fuse to form larger veins. These veins eventually lead back to the heart to complete the circuit.
During absorption, the concentration of alcohol in the arterial blood is considerably higher than the concentration of
alcohol in the venous blood. One typical study revealed a subject’s arterial blood-alcohol level to be 41 percent higher
than the venous level thirty minutes after the subject’s last drink.
2
This difference is thought to exist because of the
rapid diffusion of alcohol into the body tissues from venous blood during the early phases of absorption. Because the
administration of a blood test requires drawing venous blood from the arm, this test is clearly to the advantage of a
subject who may still be in the absorption stage. However, once absorption is complete, the alcohol becomes equally
distributed throughout the blood system.
FIGURE 12-4 The respiratory system. The trachea connects the nose and
mouth to the bronchial tubes. The bronchial tubes divide into numerous
branches that terminate in the alveoli in the lungs.
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Quick Review
• Alcohol appears in the blood within minutes after it has been taken by mouth. It slowly increases in
concentration while it is being absorbed from the stomach and the small intestine into the bloodstream.
• When all the alcohol has been absorbed, a maximum alcohol level is reached in the blood, and the
postabsorption period begins. During postabsorption, the alcohol concentration slowly decreases until a zero
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level is reached.
• Elimination of alcohol throughout the body is accomplished through oxidation and excretion. Oxidation takes
place almost entirely in the liver, whereas alcohol is excreted unchanged in the breath, urine, and perspiration.
• Breath-testing devices operate on the principle that the ratio between the concentration of alcohol in alveolar
breath and its concentration in blood is fixed.
Testing for Intoxication
From a practical point of view, drawing blood from veins of motorists suspected of being under the influence of
alcohol is simply not convenient. The need to transport each suspect to a location where a medically qualified person
can draw blood would be costly and time consuming, considering the hundreds of suspects that the average police
department must test every year. The methods used must be designed to test hundreds of thousands of motorists
annually, without causing them undue physical harm or unreasonable inconvenience, and provide a reliable diagnosis
that can be supported and defended within the framework of the legal system. This means that toxicologists have had
to devise rapid and specific procedures for measuring a driver’s degree of alcohol intoxication that can be easily
administered in the field.
BREATH TESTING FOR ALCOHOL
The most widespread method for rapidly determining alcohol intoxication is breath testing. A breath tester is simply a
device for collecting and measuring the alcohol content of alveolar breath. As we saw earlier, alcohol is expelled,
unchanged, in the breath of a person who has been drinking. A breath test measures the alcohol concentration in the
pulmonary artery by measuring its concentration in alveolar breath. Thus, breath analysis provides an easily obtainable
specimen along with a rapid and accurate result.
Breath-test results obtained during the absorption phase may be higher than results obtained from a simultaneous
analysis of venous blood. However, the former are more reflective of the concentration of alcohol reaching the brain
and therefore more accurately reflect the effects of alcohol on the subject. Again, once absorption is complete, the
difference between a blood test and a breath test should be minimal.
BREATH-TEST INSTRUMENTS
The first widely used instrument for measuring the alcohol content of alveolar breath was the Breathalyzer , developed
in 1954 by R. F. Borkenstein, who was a captain in the Indiana State Police. Starting in the 1970s, the Breathalyzer
was phased out and replaced by other instruments. Like the Breathalyzer, they assume that the ratio of alcohol in the
blood to alcohol in alveolar breath is 2,100 to 1 at a mouth temperature of 34°C. Unlike the Breathalyzer, modern
breath testers are free of chemicals. These devices include infrared light-absorption devices (described in the Closer
Analysis feature on page 296 ) and fuel cell detectors .
fuel cell detector A detector in which a chemical reaction involving alcohol produces electricity.
Infrared and fuel-cell-based breath testers are microprocessor controlled, so all an operator has to do is to press a start
button; the instrument automatically moves through a sequence of steps and produces a readout of the subject’s test
results. These instruments also perform self-diagnostic tests to ascertain whether they are in proper operating
condition.
CONSIDERATIONS IN BREATH TESTING
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An important feature of these instruments is that they can be connected to an external alcohol standard or simulator in
the form of either a liquid or a gas. The liquid simulator comprises a known concentration of alcohol in water. It is
heated to a controlled temperature and the vapor formed above the liquid is pumped into the instrument. Dry-gas
standards typically consist of a known concentration of alcohol mixed with an inert gas and compressed in cylinders.
The external standard is automatically sampled by the breath-test instrument before and/or after the subject’s breath
sample is taken and recorded. Thus the operator can check the accuracy of the instrument against the known alcohol
standard.
The key to the accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar (i.e.,
deep-lung) breath of the subject. This is typically accomplished by programming the unit to accept no less than 1.1 to
1.5 liters of breath from the subject. Also, the subject must blow for a minimum time (such as 6 seconds) with a
minimum breath flow rate (such as 3 liters per minute).
The breath-test instruments just described feature a slope detector , which ensures that the breath sample is alveolar, or
deep-lung, breath. As the subject blows into the instrument, the breath-alcohol concentration is continuously
monitored. The instrument accepts a breath sample only when consecutive measurements fall within a predetermined
rate of change. This approach ensures that the sample measurement is deep-lung breath and closely relates to the true
blood-alcohol concentration of the subject being tested.
A breath-test operator must take other steps to ensure that the breath-test result truly reflects the actual blood-alcohol
concentration within the subject. A major consideration is to avoid measuring “mouth alcohol” resulting from
regurgitation, belching, or recent intake of an alcoholic beverage. Also, recent gargling with an alcohol-containing
mouthwash can lead to the presence of mouth alcohol. As a result, the alcohol concentration detected in the exhaled
breath is higher than the concentration in the alveolar breath. To avoid this possibility, the operator must not allow the
subject to take any foreign material into his or her mouth for at least fifteen minutes before the breath test. Likewise,
the subject should be observed not to have belched or regurgitated during this period. Mouth alcohol has been shown
to dissipate after fifteen to twenty minutes from its inception.
CLOSER ANALYSIS INFRARED LIGHT ABSORPTION
In principle, infrared instruments operate no differently than the spectrophotometers described in Chapter 11 . An
evidential testing instrument that incorporates the principle of infrared light absorption is shown in Figure 1 . Any
alcohol present in the subject’s breath flows into the instrument’s breath chamber. As shown in Figure 2 , a beam of
infrared light is aimed through the chamber. A filter is used to select a wavelength of infrared light at which alcohol
will absorb. As the infrared light passes through the chamber, it interacts with the alcohol and causes the light to
decrease in intensity. The decrease in light intensity is measured by a photoelectric detector that gives a signal
proportional to the concentration of alcohol present in the breath sample. This information is processed by an
electronic microprocessor, and the percent blood-alcohol concentration is displayed on a digital readout. Also, the
blood-alcohol level is printed on a card to produce a permanent record of the test result. Most infrared breath testers
aim a second infrared beam into the same chamber to check for acetone or other chemical interferences on the breath.
If the instrument detects differences in the relative response of the two infrared beams that does not conform to ethyl
alcohol, the operator is immediately informed of the presence of an “interferant.”
FIGURE 1 An infrared breath-testing instrument—the BAC Data Master.
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Courtesy National Patent Analytical Systems, Inc., Mansfield, OH 44901
FIGURE 2 A schematic diagram of an infrared breath-testing instrument.
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CLOSER ANALYSIS THE FUEL CELL
A fuel cell converts energy arising from a chemical reaction into electrochemical energy. A typical fuel cell consists of
two platinum electrodes separated by an acid- or base-containing porous membrane. A platinum wire connects the
electrodes and allows a current to flow between them. In the alcohol fuel cell, one of the electrodes is positioned to
come into contact with a subject’s breath sample. If alcohol is present in the breath, a reaction at the electrode’s surface
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converts the alcohol to acetic acid. One by-product of this conversion is free electrons, which flow through the
connecting wire to the opposite electrode, where they interact with atmospheric oxygen to form water (see figure). The
fuel cell also requires the migration of hydrogen ions across the acidic porous membrane to complete the circuit. The
strength of the current flow between the two electrodes is proportional to the concentration of alcohol in the breath.
A detector in which chemical reactions are used to produce electricity.
Measurement of independent breath samples taken within a few minutes of each other is another extremely important
check of the integrity of the breath test. Acceptable agreement between the two tests taken minutes apart significantly
reduces the possibility of errors caused by the operator, mouth alcohol, instrument component failures, and spurious
electric signals.
FIELD SOBRIETY TESTING
A police officer who suspects that an individual is under the influence of alcohol usually conducts a series of
preliminary tests before ordering the suspect to submit to an evidential breath or blood test. These preliminary, or field,
sobriety tests are normally performed to ascertain the degree of the suspect’s physical impairment and whether an
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evidential test is justified.
Field sobriety tests usually consist of a series of psychophysical tests and a preliminary breath test (if such devices are
authorized and available for use). A portable, handheld, roadside breath tester is shown in Figure 12-5 . This device,
about the size of a pack of cigarettes, weighs 5 ounces and uses a fuel cell to measure the alcohol content of a breath
sample. The fuel cell absorbs the alcohol from the breath sample, oxidizes it, and produces an electrical current
proportional to the breath-alcohol content. This instrument can typically be used for three to five years before the fuel
cell needs to be replaced. Breath-test results obtained with devices such as those shown in Figure 12-5 must be
considered preliminary and nonevidential. They should only establish probable cause for requiring an individual to
submit to a more thorough breath or blood test.
Horizontal-gaze nystagmus, “walk and turn,” and the one-leg stand constitute a series of reliable and effective
psychophysical tests. Horizontal-gaze nystagmus is an involuntary jerking of the eye as it moves to the side. A person
experiencing nystagmus is usually unaware that the jerking is happening and is unable to stop or control it. The subject
being tested is asked to follow a penlight or some other object with his or her eye as far to the side as the eye can go.
The more intoxicated the person is, the less the eye has to move toward the side before jerking or nystagmus begins.
Usually, when a person’s blood-alcohol concentration is in the range of 0.10 percent, the jerking begins before the
eyeball has moved 45 degrees to the side (see Figure 12-6 ). Higher blood-alcohol concentration causes jerking at
smaller angles. Also, if the suspect has taken a drug that also causes nystagmus (such as phencyclidine, barbiturates,
and other depressants), the nystagmus-onset angle may occur much earlier than would be expected from alcohol alone.
FIGURE 12-5 The Alco-Sensor IV.
Courtesy Intoximeters, Inc., St. Louis, MO , www.intox.com
FIGURE 12-6 When a person’s blood-alcohol level is in the vicinity of 0.10
percent, jerking of the eye during the horizontal-gaze nystagmus test will
begin before the eyeball has moved 45 degrees to the side.
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Walk and turn and the one-leg stand are divided-attention tasks, testing the subject’s ability to comprehend and execute
two or more simple instructions at one time. The ability to understand and simultaneously carry out more than two
instructions is significantly affected by increasing blood-alcohol levels. Walk and turn requires the suspect to maintain
balance while standing heel-to-toe and at the same time listening to and comprehending the test instructions. During
the walking stage, the suspect must walk a straight line, touching heel-to-toe for nine steps, then turn around on the
line and repeat the process. The one-leg stand requires the suspect to maintain balance while standing with heels
together listening to the instructions. During the balancing stage, the suspect must stand on one foot while holding the
other foot several inches off the ground for 30 seconds; simultaneously, the suspect must count out loud during the 30-
second time period.
Quick Review
• Modern breath testers are free of chemicals. They include infrared light absorption devices and fuel cell
detectors.
• The key to the accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar
(deep-lung) breath of the subject.
• Many breath testers collect a set volume of breath and expose it to infrared light. The instrument measures the
concentration of alcohol in the collected breath sample by measuring the degree of interaction between the light
and the alcohol present.
• Law enforcement officers use field sobriety tests to estimate a motorist’s degree of physical impairment from
alcohol and to determine whether an evidential test for alcohol is justified.
• The horizontal-gaze nystagmus test, the walk and turn, and the one-leg stand are all considered reliable and
effective psychophysical tests for alcohol impairment.
Analysis of Blood for Alcohol
Gas chromatography is the approach most widely used by forensic toxicologists for determining alcohol levels in
blood. Under proper gas chromatographic conditions, alcohol can be separated from other volatile substances in the
blood. By comparing the resultant alcohol peak area to ones obtained from known blood-alcohol standards, the
investigator can calculate the alcohol level with a high degree of accuracy (see Figure 12-7 ).
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Another procedure for alcohol analysis involves the oxidation of alcohol to acetaldehyde. This reaction is carried out
in the presence of the enzyme alcohol dehydrogenase and the coenzyme nicotin-amide-adenine dinucleotide (NAD).
As the oxidation proceeds, NAD is converted into another chemical species, NADH. The extent of this conversion is
measured by a spectrophotometer and is related to alcohol concentration. This approach to blood-alcohol testing is
normally associated with instruments used in clinical or hospital settings. Instead, forensic laboratories normally use
gas chromatography for determining blood-alcohol content.
COLLECTION AND PRESERVATION OF BLOOD
Blood must always be drawn under medically acceptable conditions by a qualified individual. A nonalcoholic
disinfectant should be applied before the suspect’s skin is penetrated with a sterile needle or lancet. It is important to
eliminate any possibility that an alcoholic disinfectant could inadvertently contribute to a falsely high blood-alcohol
result. Nonalcoholic disinfectants such as aqueous benzalkonium chloride (Zepiran), aqueous mercuric chloride, or
povidone-iodine (Betadine) are recommended for this purpose.
Once blood is removed from an individual, it is best preserved sealed in an airtight container after adding an
anticoagulant and a preservative. The blood should be stored in a refrigerator until delivery to the toxicology
laboratory. The addition of an anticoagulant , such as EDTA or potassium oxalate, prevents clotting; a preservative ,
such as sodium fluoride, inhibits the growth of microorganisms capable of destroying alcohol.
anticoagulant A substance that prevents coagulation or clotting of the blood.
preservative A substance that stops the growth of microorganisms in blood.
FIGURE 12-7 A gas chromatogram showing ethyl alcohol (ethanol) in
whole blood.
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Courtesy Varian Inc., Palo Alto, CA
One study performed to determine the stability of alcohol in blood removed from living individuals found that the
most significant factors affecting alcohol’s stability in blood are storage temperature, the presence of a preservative,
and the length of storage.
3
Not a single blood specimen examined showed an increase in alcohol level with time.
Failure to keep the blood refrigerated or to add sodium fluoride resulted in a substantial decline in alcohol
concentration. Longer storage times also reduced blood-alcohol levels. Hence, failure to adhere to any of the proper
preservation requirements for blood works to the benefit of the suspect and to the detriment of society.
The collection of postmortem blood samples for alcohol-level determinations requires added precautions. Ethyl
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alcohol may be generated in the body of a deceased individual as a result of bacterial action. Therefore, it is best to
collect a number of blood samples from different body sites. For example, blood may be removed from the heart and
from the femoral vein (in the leg) and cubital vein (in the arm). Each sample should be placed in a clean, airtight
container containing an anticoagulant and sodium fluoride preservative and should be refrigerated. Blood-alcohol
levels can be attributed solely to alcohol consumption if they are nearly similar in all blood samples collected from the
same person. As an alternative to blood collection, the collection of vitreous humor and urine is recommended.
Vitreous humor and urine usually do not experience any significant postmortem ethyl alcohol production.
Quick Review
• Gas chromatography is the most widely used approach for determining blood-alcohol levels in forensic
laboratories.
• An anticoagulant should be added to a blood sample to prevent clotting; a preservative should be added to
inhibit the growth of microorganisms capable of destroying alcohol.
Alcohol and the Law
Constitutionally, every state in the United States must establish and administer statutes regulating the operation of
motor vehicles. Although such an arrangement might encourage diverse laws defining permissible blood-alcohol
levels, this has not been the case. Since the 1930s, both the American Medical Association and the National Safety
Council have exerted considerable influence in persuading the states to establish uniform and reasonable blood-alcohol
standards.
BLOOD-ALCOHOL LAWS
The American Medical Association and the National Safety Council initially recommended that a person with a blood-
alcohol concentration in excess of 0.15 percent w/v was to be considered under the influence of alcohol.
4
However,
subsequent experimental studies showed a clear correlation between drinking and driving impairment at blood-alcohol
levels much below 0.15 percent w/v. These findings eventually led to a lowering of the blood-concentration standard
for intoxication from 0.15 percent w/v to its current 0.08 percent w/v.
In 1992, the US Department of Transportation (DOT) recommended that states adopt 0.08 percent blood-alcohol
concentration as the legal measure of drunk driving. This recommendation was enacted into federal law in 2000. All
fifty states have now established per se laws , meaning that any individual meeting or exceeding a defined blood-
alcohol level (usually 0.08 percent) shall be deemed intoxicated. No other proof of alcohol impairment is necessary.
Starting in 2003, states that had not adopted the 0.08 percent per se level stood to lose part of their federal funds for
highway construction. The 0.08 percent level applies only to noncommercial drivers, as the federal government has set
the maximum allowable blood-alcohol concentration for commercial truck and bus drivers at 0.04 percent.
Several other Western countries have also set 0.08 percent w/v as the blood-alcohol level above which it is an offense
to drive a motor vehicle, including Canada, Italy, Switzerland, and the United Kingdom. Finland, France, Germany,
Ireland, Japan, the Netherlands, and Norway have a 0.05 percent limit, as do the Australian states. Sweden has lowered
its blood-alcohol concentration limit to 0.02 percent.
As shown in Figure 12-8 , a driver with a blood-alcohol level of 0.08 percent is about four times as likely to become
involved in an automobile accident than a sober individual. At the 0.15 percent level, the chances of an automobile
accident are twenty-five times higher than those for a sober driver. To estimate the relationship of blood-alcohol levels
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to body weight and the quantity of 80-proof liquor consumed, refer to Figure 12-9 .
FIGURE 12-8 A diagram of increased driving risk in relation to blood-
alcohol concentration.
Courtesy US Department of Transportation, Washington, DC
FIGURE 12-9 To use this diagram, lay a straight edge across your weight
and the number of ounces of liquor you’ve consumed on an empty or full
stomach. The point where the edge hits the right-hand column is your
maximum blood-alcohol level. The rate of elimination of alcohol from the
bloodstream is approximately 0.015 percent per hour. Therefore, to
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calculate your actual blood-alcohol level, subtract 0.015 from the number
indicated in the right-hand column for each hour from the start of
drinking.
CONSTITUTIONAL ISSUES
The Fifth Amendment to the US Constitution guarantees all citizens protection against self-incrimination —that is,
against being forced to make an admission that would prove one’s own guilt in a legal matter. Because consenting to a
breath test for alcohol might be considered a form of self-incrimination, the National Highway Traffic Safety
Administration recommended an implied-consent law to prevent a person from refusing to take a test on those
constitutional grounds. This law states that the operator of a motor vehicle on a public highway must either consent to
a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six months
to one year.
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The leading case relating to the constitutionality of collecting a blood specimen for alcohol testing, as well as obtaining
other types of physical evidence from a suspect without consent, is Schmerber v. California.
5
While being treated at a
Los Angeles hospital for injuries sustained in an automobile collision, Armando Schmerber was arrested for driving
under the influence of alcohol. Despite Schmerber’s objections, a physician took a blood sample from him at the
direction of the police department. Schmerber was convicted of driving while intoxicated, and he subsequently
appealed the decision. The case eventually reached the US Supreme Court, where Schmerber argued that his privilege
against self-incrimination had been violated by the introduction of the results of the blood test at his trial. The Court
ruled against him, reasoning that the Fifth Amendment prohibits only compelling a suspect to give testimonial
evidence that may prove to be self-incriminating; being compelled to furnish physical evidence, such as fingerprints,
photographs, measurements, and blood samples, the Court ruled, was not protected by the Fifth Amendment.
The Court also addressed the question of whether the police violated Schmerber’s Fourth Amendment protection
against unreasonable search and seizure by taking a blood specimen from him without a search warrant. The Court
upheld the constitutionality of the blood removal, reasoning that in this case the police were confronted with an
emergency situation. By the time police officials would have been able to obtain a warrant, Schmerber’s blood-alcohol
levels would have declined significantly as a result of natural body elimination processes. In effect, the evidence would
have been destroyed. The Court also emphasized that the blood specimen was taken in a medically accepted manner
and without unreasonable force. This opinion in no way condones warrantless taking of blood for alcohol or drug
testing under all circumstances. The reasonableness of actions a police officer may take to compel an individual to
yield evidence can be judged only on a case-by-case basis.
WebExtra 12.1
Calculate Your Blood-Alcohol Level www.mycrimekit.com
WebExtra 12.2
See How Alcohol Affects Your Behavior www.mycrimekit.com
Quick Review
• The current legal measure of drunk driving in the United States is a blood-alcohol concentration of 0.08
percent, or 0.08 grams of alcohol per 100 milliliters of blood.
• The implied-consent law states that the operator of a motor vehicle on a public highway must either consent to
a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six
months to one year.
Role of the Toxicologist
Once the forensic toxicologist ventures beyond the analysis of alcohol, he or she encounters an encyclopedic maze of
drugs and poisons. Even a cursory discussion of the problems and handicaps imposed on toxicologists is enough to
engender an appreciation for their accomplishments and ingenuity.
CHALLENGES FACING THE TOXICOLOGIST
The toxicologist is presented with body fluids and/or organs and asked to examine them for drugs and poisons. When
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he or she is fortunate, which is not often, some clue about the type of toxic substance present may develop from the
victim’s symptoms, a postmortem pathological examination, an examination of the victim’s personal effects, or the
nearby presence of empty drug containers or household chemicals. Without such supportive information, the
toxicologist must use general screening procedures with the hope of narrowing thousands of possibilities to one.
If this task does not seem monumental, consider that the toxicologist is not dealing with drugs at the concentration
levels found in powders and pills. By the time a drug specimen reaches the toxicology laboratory, it has been
dissipated and distributed throughout the body. The drug analyst may have gram or milligram quantities of material to
work with, but the toxicologist must be satisfied with amounts in nanograms or, at best, micrograms, acquired only
after being carefully extracted from body fluids and organs.
Furthermore, the body is an active chemistry laboratory, and no one can appreciate this observation more than a
toxicologist. Few substances enter and completely leave the body in the same chemical state. The drug that is injected
is not always the substance extracted from the body tissues. Therefore, a thorough understanding of how the body
alters or metabolizes the chemical structure of a drug is essential in detecting its presence.
It would, for example, be futile and frustrating to search exhaustively for heroin in the human body. This drug is
almost immediately metabolized to morphine on entering the bloodstream. Even with this information, the search may
still prove impossible unless the examiner also knows that only a small percentage of morphine is excreted unchanged
in urine. For the most part, morphine becomes chemically bonded to body carbohydrates before being eliminated in
urine. Thus, successful detection of morphine requires that its extraction be planned in accordance with a knowledge of
its chemical fate in the body.
Another example of why a toxicologist needs to know how different drugs metabolize in the body is provided by the
investigation of the death of Anna Nicole Smith. In her case, the sedative chloral hydrate was a major contributor to
her death, but its presence was confirmed by detecting its active metabolite, trichloroethanol (see the Case File on page
306 ).
Last, when and if the toxicologist has surmounted all of these obstacles and has finally detected, identified, and
quantitated a drug or poison, he or she must assess the substance’s toxicity. Fortunately, there is published information
relating to the toxic levels of most drugs. However, even when such data are available, their interpretation must
assume that the victim’s physiological behavior agrees with that of subjects of previous studies. Such an assumption
may not be entirely valid without knowing the subject’s case history. No experienced toxicologist would be surprised
to find an individual tolerating a toxic level of a drug that would have killed most other people.
COLLECTION AND PRESERVATION OF TOXICOLOGICAL
EVIDENCE
The toxicologist’s capabilities depend directly on input from the attending physician, medical examiner, and police
investigator. It is a tribute to forensic toxicologists, who often must labor under conditions that do not afford such
cooperation, that they can achieve the high level of proficiency that they do.
Generally, when questions about drug use involve a deceased person, the medical examiner decides what biological
specimens must be shipped to the toxicology laboratory for analysis. However, a living person suspected of being
under the influence of a drug presents a completely different problem, and few options are available. In this case, an
entire urine void (i.e., urine sample) is collected and submitted for toxicological analysis. Preferably, two consecutive
voids should be collected in separate specimen containers.
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CASE FILES CELEBRITY TOXICOLOGY: MICHAEL JACKSON—
THE DEMISE OF A SUPERSTAR
A call to 911 had the desperate tone of urgency. The voice of a young man implored an ambulance to hurry to the
home of pop star Michael Jackson. The unconscious performer was in cardiac arrest and was not responding to CPR.
The 50-year-old Jackson was pronounced dead on arrival at a regional medical center. When the initial autopsy results
revealed no signs of foul play, rumors immediately began to swirl around a drug-related death. News media coverage
showed investigators carrying bags full of medical supplies out of the Jackson residence. Therefore, it came as no
surprise when the forensic toxicology report accompanying Jackson’s autopsy showed that the entertainer had died of a
drug overdose.
Apparently, Jackson had become accustomed to receiving sedatives to help him sleep. On the morning of his death, his
physician stated that he administered valium to Mr. Jackson. Further, at 2 a.m., he administered the sedative
lorazepam, and at 3 a.m. the physician administered another sedative, midazolam. Those drugs were administered
again at 5 a.m. and 7:30 a.m., but Mr. Jackson still was unable to sleep. Finally, at about 10:40 a.m., Jackson’s doctor
gave him 25 milligrams of propofol, at which point Mr. Jackson went to sleep. Propofol is a powerful sedative that is
principally used for the maintenance of surgical anesthesia. All of the drugs administered to Jackson were sedatives
that act in concert to depress the activities of the central nervous system, so it comes as no surprise that this drug
cocktail resulted in cardiac arrest and death.
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Michael Jackson Justin Sullivan/Pool\AP Wide World Photos
When a licensed physician or registered nurse is available, a sample of blood should also be collected. The amount of
blood taken depends on the type of examination to be conducted. Comprehensive toxicological tests for drugs and
poisons can conveniently be carried out on a minimum of 10 milliliters of blood. A determination solely for the
presence of alcohol will require much less—approximately 5 milliliters of blood. However, many therapeutic drugs,
such as tranquilizers and barbiturates, taken in combination with a small, non-intoxicating amount of alcohol, produce
behavioral patterns resembling alcohol intoxication. For this reason, the toxicologist must be given enough blood to
perform a comprehensive analysis for drugs in cases in which only low alcohol concentrations are discovered.
TECHNIQUES USED IN TOXICOLOGY
For the toxicologist, the upsurge in drug use and abuse has meant that the overwhelming majority of fatal and nonfatal
toxic agents are drugs. Not surprisingly, a relatively small number of drugs—namely, those discussed in Chapter 11 —
compose nearly all the toxic agents encountered. Of these, alcohol, marijuana, and cocaine account for at least 90
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percent of the drugs encountered by toxicologists in a typical toxicology laboratory.
CASE FILES ACCIDENTAL OVERDOSE: THE TRAGEDY OF ANNA
NICOLE SMITH
Rumors exploded in the media when former model, Playboy playmate, reality television star, and favorite tabloid
subject Anna Nicole Smith was found unconscious at age 39 in her hotel room at the Seminole Hard Rock Hotel &
Casino in Hollywood, Florida. She was taken to Memorial Legal Hospital, where she was declared dead. Postmortem
analysis of Smith’s blood revealed an array of prescribed medications. Most pronounced was a toxic level of a
metabolite of the sedative chloral hydrate. Some of the contents of the toxicology report from Smith’s autopsy are
shown here.
Anna Nicole Smith Manuel Balce Ceneta / PA Photos\Landov Media
FINAL PATHOLOGICAL DIAGNOSES
I. ACUTE COMBINED DRUG INTOXICATION
A. Toxic/legal drug: Chloral Hydrate (Noctec)
1. Trichloroethanol (TCE) 75 mg/L (active metabolite)
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2. Trichloroacetic acid (TCA) 85 mg/L (inactive metabolite)
B. Therapeutic drugs:
1. Diphenhydramine (Benadryl) 0.11 mg/L
2. Clonazepam (Klonopin) 0.04 mg/L
3. Diazepam (Valium) 0.21 mg/L
4. Nordiazepam (metabolite) 0.38 mg/L
5. Temazepam (metabolite) 0.09 mg/L
6. Oxazepam 0.09 mg/L
7. Lorazepam 0.022 mg/L
C. Other non-contributory drugs present (atropine, topiramate, ciprofloxacin, acetaminophen)
Although many of the drugs present were detected at levels consistent with typical doses of the prescribed
medications, it was their presence in combination with chloral hydrate that exacerbated the toxic level of chloral
hydrate. The lethal combination of these prescription drugs caused failure of both her circulatory and respiratory
systems and resulted in her death. The investigators determined that the overdose of chloral hydrate and other drugs
was accidental and not a suicide. This was because of the nonexcessive levels of most of the prescription medications
and the discovery of a significant amount of chloral hydrate still remaining in its original container; had she intended
to kill herself, she probably would have ingested it all. Anna Nicole Smith was a victim of accidental overmedication.
ACIDS AND BASES
Like the drug analyst, the toxicologist must devise an analytical scheme to detect, isolate, and identify a toxic
substance. The first chore is to remove and isolate drugs and other toxic agents from the biological materials submitted
as evidence. Because drugs constitute a large portion of the toxic materials found, a good deal of effort must be
devoted to their extraction and detection. So many different procedures are used that a useful description of them
would be too detailed for this text. We can best understand the underlying principle of drug extraction by observing
that many drugs fall into the categories of acids and bases .
acid A compound capable of donating a hydrogen ion (H
+
) to another compound.
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base A compound capable of accepting a hydrogen ion (H+).
By controlling the acidity or basicity (i.e., pH ) of a water solution into which blood, urine, or tissues are dissolved, the
toxicologist can control the type of drug that is recovered. For example, acidic drugs are easily extracted from an
acidified water solution (i.e., with a pH of less than 7) with organic solvents such as chloroform. Similarly, basic drugs
are readily removed from a basic water solution (i.e., with a pH of greater than 7) with organic solvents. This simple
approach gives the toxicologist a general technique for extracting and categorizing drugs. Some of the more commonly
encountered drugs may be classified as follows:
pH A symbol used to express the basicity or acidity of a substance. A pH of 7 is neutral; lower values are acidic, and
higher values are basic.
Acid Drugs Basic Drugs
Barbiturates Phencyclidine
Acetylsalicylic acid (aspirin) Methadone
Amphetamines
Cocaine
FIGURE 12-10 Biological fluids and tissues are extracted for acidic and
basic drugs by controlling the pH of a water solution in which they are
dissolved. Once this is accomplished, the toxicologist analyzes for drugs by
using screening and confirmation test procedures.
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SCREENING AND CONFIRMATION
Once the specimen has been extracted and divided into acidic and basic fractions, the toxicologist can identify the
drugs present. The strategy for identifying abused drugs entails a two-step approach: screening and confirmation (see
Figure 12-10 ). A screening test normally gives quick insight into the likelihood that a specimen contains a drug
substance. This test allows a toxicologist to examine a large number of specimens within a short period of time for a
wide range of drugs. Any positive results from a screening test are tentative at best and must be verified with a
confirmation test.
Screening Tests.
The three most widely used screening tests are thin-layer chromatography (TLC), gas chromatography (GC), and
immunoassay. The techniques of GC and TLC were described in Chapter 10 . The third technique, immunoassay, has
proved to be a useful screening tool in toxicology laboratories. Its principles are very different from any of the
analytical techniques we have discussed so far. Basically, immunoassay is based on specific drug antibody reactions.
We will learn about this concept in Chapter 15 . The primary advantage of immunoassay is its ability to detect small
concentrations of drugs in body fluids and organs. In fact, this technique provides the best approach for detecting the
low drug levels normally associated with smoking marijuana.
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Confirmation Tests.
A positive screening test may be due to a substance’s close chemical structure to an abused drug. For this reason, the
toxicologist must follow up any positive screening test with a confirmation test. Because of the potential legal impact
of the results of a drug finding on an individual, only the most conclusive confirmation procedures should be used.
FIGURE 12-11 The combination of the gas chromatograph and the mass
spectrometer enables forensic toxicologists to separate the components of a
drug mixture and enables the specific identification of a drug substance.
Gas chromatography/mass spectrometry is generally accepted as the confirmation test of choice. As we learned in
Chapter 11 , the combination of gas chromatography and mass spectrometry provides a one-step confirmation test of
unequaled sensitivity and specificity. Figure 12-11 illustrates the process. After being introduced to the gas
chromatograph, the sample is separated into its components. When the separated sample component leaves the column
of the gas chromatograph, it enters the mass spectrometer, where it is bombarded with high-energy electrons. This
bombardment causes the sample to break up into fragments, producing a fragmentation pattern, or mass spectrum, for
each sample. For most compounds, the mass spectrum represents a unique pattern that can be used for identification.
There is tremendous interest in drug-testing programs for use not only in criminal matters but in industry and
government as well. Submitting job applicants and employees in the workplace to urine testing for drugs is becoming
common practice. Likewise, the US military has an extensive urine-testing program for its members. Many urine-
testing programs rely on private laboratories to perform the required analyses. In any case, when the drug-test results
may form the basis for taking action against an individual, both a screening and confirmation test must be incorporated
into the testing protocol to ensure the integrity of the laboratory’s conclusions.
DETECTING DRUGS IN HAIR
When a forensic toxicological examination on a living person is required, the interests of speed and practicality limit
the specimens taken to blood and urine. Most drugs remain in the bloodstream for about 24 hours; in urine, they
normally are present for up to 72 hours. However, it may be necessary to go farther back in time to ascertain whether a
subject has been abusing a drug. If so, the only viable alternative to blood and urine specimens is head hair.
Hair is nourished by blood flowing through capillaries located close to the hair root. Drugs present in blood diffuse
through the capillary walls into the base of the hair and become permanently entrapped in the hair’s hardening protein
structure. As the hair continues to grow, the drug’s location on the hair shaft becomes a historical marker for
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delineating the onset of drug intake. Given that the average human head hair grows at the rate of 1 centimeter per
month, analyzing segments of hair for drug content may define the timeline of drug use, tracing it back over a period
of weeks, months, or possibly years, depending on the hair’s length.
However, caution is required in interpreting the timeline. The chronology of drug intake may be distorted by drugs that
have penetrated the hair’s surface as a result of environmental exposure or by drugs that have entered the hair’s surface
through sweat. Nevertheless, drug hair analysis is the only viable approach for measuring long-term abuse of a drug.
DETECTING NONDRUG POISONS
Although forensic toxicologists devote most of their efforts to detecting drugs, they also test for a wide variety of other
toxic substances. Some of these are rare elements, not widely or commercially available. Others are so common that
virtually everyone is exposed to nontoxic amounts of them every day.
Heavy Metals.
One group of poisons once commonly encountered in criminal cases of murder are known as heavy metals . They
include arsenic, bismuth, antimony, mercury, and thallium. These days, however, the forensic toxicologist only
occasionally encounters heavy metals because severe environmental protection regulations restrict their availability to
the general public. Nevertheless, as the following Case File makes clear, their use is by no means only a historical
curiosity.
To screen for many of these metals, the investigator may dissolve the suspect body fluid or tissue in a hydrochloric
acid solution and insert a copper strip into the solution. This process is known as the Reinsch test. The appearance of a
silvery or dark coating on the copper indicates the presence of a heavy metal. Such a finding must be confirmed by
analytical techniques suitable for inorganic analysis—namely, emission spectroscopy, or X-ray diffraction.
CASE FILES JOANN CURLEY: CAUGHT BY A HAIR
A vibrant young woman named Joann Curley rushed to the Wilkes-Barre (Pennsylvania) General Hospital—her
husband, Bobby, required immediate medical attention. Bobby was experiencing a burning sensation in his feet,
numbness in his hands, a flushed face, and intense sweating. After being discharged, Bobby experienced another bout
of debilitating pain and numbness. He was admitted to another hospital. There doctors observed extreme alopecia, or
hair loss.
Test results of Bobby’s urine showed high levels of the heavy metal thallium in his body. Thallium, a rare and highly
toxic metal that was used decades ago in substances such as rat poison and to treat ringworm and gout, was found in
sufficient quantities to cause Bobby’s sickness. The use of thallium had been banned in the United States in 1984.
Now, at least, Bobby could be treated. However, before Bobby’s doctors could begin treating him for thallium
poisoning, he experienced cardiac arrest and slipped into a coma. Joann Curley made the difficult decision to remove
her husband of thirteen months from life-supporting equipment. He died shortly thereafter.
Investigators learned that Bobby had changed his life insurance to list his wife, Joann, as the beneficiary of his
$300,000 policy. Based on this information, police consulted a forensic toxicologist in an effort to glean as much from
the physical evidence in Bobby Curley’s body as possible. The toxicologist conducted segmental analysis of Bobby’s
hair, an analytical method based on the predictable rate of hair growth on the human scalp: an average of 1 centimeter
per month. Bobby’s hair was approximately 5 inches (12.5 centimeters) long, which represents almost twelve months
of hair growth. Each section tested represented a specific period of time in the final year of Bobby’s life.
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The hair analysis confirmed that Bobby Curley had been poisoned with thallium. The first few doses were small,
which probably barely made him feel sick at the time. Gradually, over a year or more, Bobby was receiving more
doses of thallium until he finally succumbed to a massive dose three or four days before his death. After careful
scrutiny of the timeline, investigators concluded that only Joann Curley had access to Bobby during each of these
intervals. She also had motive, in the amount of $300,000.
Presented with the timeline and the solid toxicological evidence against her, Joann Curley pleaded guilty to murder. As
part of her plea agreement, she provided a forty-page written confession of how she haphazardly dosed Bobby with rat
poison she had found in her basement. She admitted that she murdered him for the money she would receive from
Bobby’s life insurance policy.
Carbon Monoxide.
Unlike heavy metals, carbon monoxide is still one of the most common poisons encountered in a forensic laboratory.
Inhaling the carbon monoxide from automobile exhaust fumes is a relatively common way to commit suicide (see
Figure 12-12 ). The victim typically uses a garden or vacuum cleaner hose to connect the tailpipe with the vehicle’s
interior or allows the engine to run in a closed garage: A level of carbon monoxide sufficient to cause death
accumulates in five to ten minutes in a closed single-car garage.
When carbon monoxide enters the human body, it is primarily absorbed by the red blood cells, where it combines with
hemoglobin to form carboxyhemoglobin. An average red blood cell contains about 280 million molecules of
hemoglobin. Oxygen normally combines with hemoglobin, which transports the oxygen throughout the body.
However, if a high percentage of the hemoglobin combines with carbon monoxide, not enough is left to carry
sufficient oxygen to the tissues, and death by asphyxiation quickly follows.
There are two basic methods for measuring the concentration of carbon monoxide in the blood: Spectrophotometric
methods examine the visible spectrum of blood to determine the amount of carboxyhemoglobin relative to
oxyhemoglobin or total hemoglobin. Alternatively, a volume of blood can be treated with a reagent to liberate the
carbon monoxide, which is then measured by gas chromatography.
The amount of carbon monoxide in blood is generally expressed as percent saturation . This represents the extent to
which the available hemoglobin has been converted to carboxyhemoglobin. The transition from normal or
occupational levels of carbon monoxide to toxic levels is not sharply defined. It varies with, among other things, the
age, health, and general fitness of each individual. In a healthy middle-age individual, a carbon monoxide blood
saturation greater than 50 to 60 percent is considered fatal. However, in combination with alcohol or other depressants,
fatal levels may be significantly lower. For instance, a carbon monoxide saturation of 35 to 40 percent may prove fatal
in the presence of a blood-alcohol concentration of 0.20 percent w/v. Interestingly, chain smokers may have a constant
carbon monoxide level of 8 to 10 percent in normal circumstances because of the carbon monoxide present in cigarette
smoke.
FIGURE 12-12 Intentionally inhaling carbon monoxide fumes from an
automobile is a common way to commit suicide.
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© Dorling Kindersley
The level of carbon monoxide in the blood of a victim found dead at the scene of a fire can help ascertain whether foul
play has occurred. High levels of carbon monoxide in the blood prove that the victim breathed the combustion
products of the fire and was therefore alive when the fire began. By contrast, low levels of carbon monoxide indicate
that the victim was probably dead before the fire started, and may have been deliberately placed at the scene in order to
destroy the body. Many attempts at covering up a murder by setting fire to a victim’s house or car have been uncovered
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in this manner.
SIGNIFICANCE OF TOXICOLOGICAL FINDINGS
Once a drug is found and identified, the toxicologist assesses its influence on the behavior of the individual.
Interpreting the results of a toxicology finding is one of the toxicologist’s most difficult chores. Recall that many
countries have designated a specific blood-alcohol level at which an individual is deemed to be under the influence of
alcohol. These levels were established as a result of numerous studies conducted over several years to measure the
effects of alcohol levels on driving performance. However, no such legal guidelines are available to the toxicologist
who must judge how a drug other than alcohol affects an individual’s performance or physical state.
For many drugs, blood concentration levels are readily determined and can be used to estimate the pharmacological
effects of the drug on the individual. Often, when dealing with a living person, the toxicologist has the added benefit of
knowing what a police officer may have observed about an individual’s behavior and motor skills. For a deceased
person, drug levels in various body organs and tissues provide additional information about the individual’s state at the
time of death. However, before drawing conclusions about drug-induced behavior, the analyst must consider other
factors, including the age, physical condition, and tolerance of the drug user.
With prolonged use of a drug, an individual may become less responsive to a drug’s effects and tolerate blood
concentrations of the drug that would kill a casual drug user. Therefore, knowledge of an individual’s history of drug
use is important in evaluating drug concentrations. Another consideration is the additive or synergistic effects of the
interaction of two or more drugs, which may produce a highly intoxicated or comatose state even though none of the
drugs alone is present in high or toxic levels. The combination of alcohol with barbiturates or narcotics is a common
example of a potentially lethal drug combination.
The amount of a drug in urine is a poor indicator of how extensively an individual’s behavior or state is influenced by
the drug. Urine is formed outside the body’s circulatory system, and consequently drug levels can build up in it over a
relatively long period of time. Some drugs are found in the urine one to three days after they have been taken and long
after their effects on the user have disappeared. Nevertheless, the value of this information should not be discounted.
Urine drug levels, like blood levels, are best used by law enforcement authorities and the courts to corroborate other
investigative and medical findings regarding an individual’s condition. Hence, for an individual arrested under
suspicion of being under the influence of a drug, a toxicologist’s determinations supplement the observations of the
arresting officer, including the results of field sobriety tests and a drug influence evaluation (discussed in the following
section).
For a deceased person, the medical examiner or coroner must establish a cause of death. However, before a conclusive
determination is made, the examining physician depends on the forensic toxicologist to demonstrate the presence or
absence of a drug or poison in the tissues or body fluids of the deceased. Only through the combined efforts of the
toxicologist and the medical examiner or coroner can society be assured that death investigations achieve high
professional and legal standards.
Drug Recognition Experts
Although recognizing alcohol-impaired performance is an expertise generally accorded to police officers by the courts,
recognizing drug-induced intoxication is much more difficult and generally not part of police training. During the
1970s, the Los Angeles Police Department developed and tested a series of clinical and psychophysical examinations
that a trained police officer can use to identify and differentiate among types of drug impairment. This program has
evolved into a national program to train police as drug recognition experts . Normally, a three- to five-month training
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program is required to certify an officer as a drug recognition expert (DRE).
CASE FILES DEATH BY RADIATION POISONING
In November 2006, Alexander V. Litvinenko lay at death’s doorstep in a London hospital. He was in excruciating pain
and had symptoms that included hair loss, an inability to make blood cells, and gastrointestinal distress. His organs
slowly failed as he lingered for three weeks before dying. British investigators soon confirmed that Litvinenko died
from the intake of polonium 210, a radioactive element, in what appeared to be its first use as a murder weapon.
Litvinenko’s death almost immediately set off an international uproar. Litvinenko, a former KBG operative, had
became a vocal critic of the Russian spy agency FSB, the domestic successor to the KGB. In 2000, he fled to London,
where he was granted asylum. Litvinenko had continued to voice his criticisms of the Russian president, Vladimir
Putin. Just before his death, Litvinenko was believed to have compiled, on behalf of a British company looking to
invest millions in a project in Russia, an incriminating report regarding the activities of senior Kremlin officials.
Suspicions immediately fell on Andrei Lugovoi and Dmitri Kovtun, business associates of Mr. Litvinenko. Lugovoi
was himself a former KGB officer. On the day he fell ill, Litvinenko had met Lugovoi and Kovtun at the Pine Bar of
the Millennium Hotel in London. At the meeting, Mr. Litvinenko drank tea out of a teapot later found to be highly
radioactive. British officials have accused Lugovoi of poisoning Litvinenko. Although the precise nature of the
evidence against him still has not been made clear, investigators have linked him and Mr. Kovtun to a trail of polonium
210 radioactivity in hotel rooms, restaurants, bars, and offices stretching from London to Hamburg, Germany, as well
as in British Airways planes that had flown to Moscow. Each man has denied killing Mr. Litvinenko.
Polonium 210 is highly radioactive and very toxic. By weight, it is about 250 million times as toxic as cyanide, so a
particle the size of a few grains of sand could be fatal. It emits a radioactive ray known as an alpha particle. Because
this form of radiation cannot penetrate the skin, polonium 210 can only be effective as a poison if it is swallowed,
breathed in, or injected. The particles disperse through the body and first destroy fast-growing cells such as those in
bone marrow, blood, hair, and the digestive tract. This is consistent with Mr. Litvinenko’s symptoms. There is no
antidote for polonium poisoning.
Polonium does have industrial uses and is produced by commercial or institutional nuclear reactors. Polonium 210 has
been found to be ideal for making antistatic devices that remove dust from film and lenses, as well as from the
atmosphere of paper and textile plants. Its non-body-penetrating rays produce an electric charge on nearby air. Bits of
dust with static attract the charged air, which neutralizes them. Once free of static, the dust is easy to blow or brush
away. Manufacturers of such antistatic devices take great pains to make the polonium hard to remove from their
products.
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Alexander Litvinenko, former KGB agent, before and after he became sick.
(left) Alistair Fuller\AP Wide World Photos; (right) Natasja Weitsz\Getty Images, Inc.-Getty News
The DRE program incorporates standardized methods for examining suspects to determine whether they have taken
one or more drugs. The process is systematic and standard: To ensure that each subject has been tested in a routine
fashion, each DRE must complete a standard Drug Influence Evaluation form (see Figure 12-13 ). The entire drug
evaluation takes approximately thirty to forty minutes. The components of the twelve-step process are summarized in
Table 12.1 .
FIGURE 12-13 Drug Influence Evaluation form.
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US National Highway Traffic Safety Administration, Aug., 1999
TABLE 12.1 Components of the Drug Recognition Process
1. Breath-Alcohol Test . By obtaining an accurate and immediate measurement of the suspect’s blood-alcohol
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concentration, the drug recognition expert (DRE) can determine whether alcohol may be contributing to the
suspect’s observable impairment and whether the concentration of alcohol is sufficient to be the sole cause of
that impairment.
2. Interview with the Arresting Officer . Spending a few minutes with the arresting officer often enables the DRE
to determine the most promising areas of investigation.
3. Preliminary Examination . This structured series of questions, specific observations, and simple tests provides
the first opportunity to examine the suspect closely. It is designed to determine whether the suspect is suffering
from an injury or from another condition unrelated to drug consumption. It also affords an opportunity to begin
assessing the suspect’s appearance and behavior for signs of possible drug influence.
4. Eye Examination . Certain categories of drugs induce nystagmus, an involuntary, spasmodic motion of the
eyeball. Nystagmus is an indicator of drug-induced impairment. The inability of the eyes to converge toward
the bridge of the nose also indicates the possible presence of certain types of drugs.
5. Divided-Attention Psychophysical Tests . These tests check balance and physical orientation and include the
walk and turn, the one-leg stand, the Romberg balance, and the finger-to-nose.
6. Vital Signs Examinations . Precise measurements of blood pressure, pulse rate, and body temperature are
taken. Certain drugs elevate these signs; others depress them.
7. Dark Room Examinations . The size of the suspect’s pupils in room light, near-total darkness, indirect light,
and direct light is checked. Some drugs cause the pupils to either dilate or constrict.
8. Examination for Muscle Rigidity . Certain categories of drugs cause the muscles to become hypertense and
quite rigid. Others may cause the muscles to relax and become flaccid.
9. Examination for Injection Sites . Users of certain categories of drugs routinely or occasionally inject their
drugs. Evidence of needle use may be found on veins along the neck, arms, and hands.
10. Suspect’s Statements and Other Observations . The next step is to attempt to interview the suspect
concerning the drug or drugs he or she has ingested. Of course, the interview must be conducted in full
compliance of the suspect’s constitutional rights.
11. Opinions of the Evaluator . Using the information obtained in the previous ten steps, the DRE is able to
make an informed decision about whether the suspect is impaired by drugs and, if so, what category or
combination of categories is the probable cause of the impairment.
12. Toxicological Examination . The DRE should obtain a blood or urine sample from the suspect for laboratory
analysis in order to secure scientific, admissible evidence to substantiate his or her conclusions.
The DRE evaluation process can suggest the presence of the following seven broad categories of drugs:
1. Central nervous system depressants
2. Central nervous system stimulants
3. Hallucinogens
4. Dissociative anesthetics (includes phencyclidine and its analogs)
5. Inhalants
6. Narcotic analgesics
7. Cannabis
The DRE program is not designed to be a substitute for toxicological testing. The toxicologist can often determine that
a suspect has a particular drug in his or her body, but the toxicologist often cannot infer with reasonable certainty that
the suspect was impaired at a specific time. On the other hand, the DRE can supply credible evidence that the suspect
was impaired at a specific time and that the nature of the impairment was consistent with a particular family of drugs.
However, the DRE program usually cannot determine which specific drug was ingested. Proving drug intoxication
requires a coordinated effort and the production of competent data from both the DRE and the forensic toxicologist.
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Quick Review
• The forensic toxicologist must devise an analytical scheme to detect, isolate, and identify toxic drug substances
extracted from biological fluids, tissues, and organs.
• A screening test gives quick insight into the likelihood that a specimen contains a drug substance. Positive
results arising from a screening test are tentative at best and must be verified with a confirmation test.
• The most widely used screening tests are thin-layer chromatography, gas chromatography, and immunoassay.
Gas chromatography/mass spectrometry is generally accepted as the confirmation test of choice.
• Once a drug is extracted and identified, a toxicologist may be required to judge the drug’s effect on an
individual’s natural performance or physical state.
• A three- to five-month training program is required to certify an officer as a drug recognition expert (DRE).
This training incorporates standardized methods for examining suspects to determine whether they have taken
one or more drugs.
Virtual Lab Blood Alcohol Analysis
To perform a virtual blood alcohol analysis, go to www.pearsoncustom.com/us/vlm/
CHAPTER REVIEW
• Forensic toxicologists detect and identify drugs and poisons in body fluids, tissues, and organs in situations that
involve violations of criminal laws.
• Ethyl alcohol is the most heavily abused drug in Western countries.
• Alcohol appears in the blood within minutes after it has been taken by mouth. It slowly increases in
concentration while it is being absorbed from the stomach and the small intestine into the bloodstream.
• When all the alcohol has been absorbed, a maximum alcohol level is reached in the blood, and the
postabsorption period begins. During postabsorption, the alcohol concentration slowly decreases until a zero
level is reached.
• Elimination of alcohol throughout the body is accomplished through oxidation and excretion. Oxidation takes
place almost entirely in the liver, whereas alcohol is excreted unchanged in the breath, urine, and perspiration.
• Breath-testing devices operate on the principle that the ratio between the concentration of alcohol in alveolar
breath and its concentration in blood is fixed.
• Modern breath testers are free of chemicals. They include infrared light absorption devices and fuel cell
detectors.
• The key to the accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar
(deep-lung) breath of the subject.
• Many breath testers collect a set volume of breath and expose it to infrared light. The instrument measures the
concentration of alcohol in the collected breath sample by measuring the degree of interaction between the light
and the alcohol present.
• Law enforcement officers use field sobriety tests to estimate a motorist’s degree of physical impairment from
alcohol and to determine whether an evidential test for alcohol is justified.
• The horizontal-gaze nystagmus test, the walk and turn, and the one-leg stand are all considered reliable and
effective psychophysical tests for alcohol impairment.
• Gas chromatography is the most widely used approach for determining blood-alcohol levels in forensic
laboratories.
• An anticoagulant should be added to a blood sample to prevent clotting; a preservative should be added to
inhibit the growth of microorganisms capable of destroying alcohol.
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• The current legal measure of drunk driving in the United States is a blood-alcohol concentration of 0.08
percent, or 0.08 grams of alcohol per 100 milliliters of blood.
• The implied-consent law states that the operator of a motor vehicle on a public highway must either consent to
a test for alcohol intoxication, if requested, or lose his or her license for some designated period—usually six
months to one year.
• The forensic toxicologist must devise an analytical scheme to detect, isolate, and identify toxic drug substances
extracted from biological fluids, tissues, and organs.
• A screening test gives quick insight into the likelihood that a specimen contains a drug substance. Positive
results arising from a screening test are tentative at best and must be verified with a confirmation test.
• The most widely used screening tests are thin-layer chromatography, gas chromatography, and immunoassay.
Gas chromatography/mass spectrometry is generally accepted as the confirmation test of choice.
• Once a drug is extracted and identified, a toxicologist may be required to judge the drug’s effect on an
individual’s natural performance or physical state.
• A three- to five-month training program is required to certify an officer as a drug recognition expert (DRE).
This training incorporates standardized methods for examining suspects to determine whether they have taken
one or more drugs.
KEY TERMS
absorption 291
acid 306
alveoli 293
anticoagulant 300
artery 292
base 306
capillary 292
excretion 291
fuel cell detector 295
metabolism 290
oxidation 291
pH 306
preservative 300
toxicologist 290
vein 292
REVIEW QUESTIONS
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1.
The _________ studies body fluids, tissues, and organs to detect and identify drugs and poisons.
2.
True or False: Toxicologists are employed only by crime laboratories. _________
3.
The most heavily abused drug in the Western world is __________.
4.
The transformation of chemicals introduced into the body into substances that are easier to eliminate is called
___________.
5.
Alcohol consumed on an empty stomach is absorbed (faster, slower) than an equivalent amount of alcohol taken when
there is food in the stomach.
6.
Alcohol is eliminated from the body by _________ and _________.
7.
Approximately 98 percent of the ethyl alcohol consumed is oxidized to carbon dioxide and water in the _________.
8.
The amount of alcohol exhaled in the _________ is directly proportional to the concentration of alcohol in the blood.
9.
Alcohol is eliminated from the blood at an average rate of _________ percent w/v.
10.
True or False: The amount of alcohol in the blood is not directly proportional to the concentration of alcohol in the
brain. _________
11.
True or False: Blood-alcohol levels have become the accepted standard for relating alcohol intake to its effect on the
body. ___________
12.
Under normal drinking conditions, alcohol concentration in the blood peaks in _________ to _________ minutes.
13.
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A(n) _________ carries blood away from the heart; a(n) _________ carries blood back to the heart.
14.
The _________ artery carries deoxygenated blood from the heart to the lungs.
15.
Alcohol passes from the blood capillaries into the _________ sacs in the lungs.
16.
One milliliter of blood contains the same amount of alcohol as approximately _________ milliliters of alveolar breath.
17.
True or False: When alcohol is being absorbed into the blood, the alcohol concentration in venous blood is higher than
that in arterial blood. _________
18.
True or False: Portable, handheld, roadside breath testers for alcohol provide evidential test results. _________
19.
Most modern breath testers use _________ radiation to detect and measure alcohol in the breath.
20.
In an alcohol _________, two platinum electrodes are separated by an acid- or base-containing porous membrane, and
one of the electrodes is positioned to come into contact with a subject’s breath sample.
21.
To avoid the possibility of testing “mouth alcohol,” the operator of a breath tester must not allow the subject to take
any foreign materials into the mouth for _________ to _________ minutes prior to the test.
22.
True or False: A series of reliable and effective psychophysical tests are the horizontal-gaze nystagmus, the walk and
turn, and the one-leg stand. _________
23.
Alcohol can be separated from other volatiles in blood and measured by the technique of _________.
24.
When drawing blood for alcohol testing, the breath-test operator must first wipe the suspect’s skin with a(n)
_________ disinfectant.
25.
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True or False: Failure to add a preservative, such as sodium fluoride, to blood removed from a living person may lead
to a decline in alcohol concentration. _________
26.
Most states have established _________ percent w/v as the impairment limit for blood-alcohol concentration in
noncommercial drivers.
27.
Studies show that an individual is about _________ times as likely to become involved in an automobile accident at
the legal limit for blood alcohol as a sober individual.
28.
In the case of _________, the Supreme Court ruled that taking nontestimonial evidence, such as a blood sample, did
not violate a suspect’s Fifth Amendment rights.
29.
After entering the body, heroin is changed into _________.
30.
The body fluids _________ and _________ are both desirable for the toxicological examination of a living person
suspected of being under the influence of a drug.
31.
A large number of drugs can be classified chemically as _________ or _________.
32.
True or False: Water with a pH value of less than 7 is basic. ___________
33.
Drugs are extracted from body fluids and tissues by carefully controlling the _________ of the medium in which the
sample has been dissolved.
34.
Both _________ and _________ tests must be incorporated into the drug-testing protocol of a toxicology laboratory to
ensure the correctness of the laboratory’s conclusions.
35.
The most widely used screening tests used by toxicologists are _________, _________, and ____________.
36.
The preferred method for confirmation testing is a combination of _________ and _________, which creates a unique
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pattern that can be used for identification.
37.
A toxicologist may be able to detect and identify a long-abused drug or poison because drugs present in blood diffuse
through capillary walls into the base of a(n) _________ and become permanently entrapped in its hardening protein
structure.
38.
The gas _________ combines with hemoglobin in the blood to form carboxyhemoglobin, thus interfering with the
transportation of oxygen in the blood.
39.
True or False: Blood levels of drugs can be used alone to draw definitive conclusions about the effects of a drug on an
individual. _________
40.
True or False: The level of a drug present in the urine is by itself a poor indicator of how extensively an individual is
affected by a drug. _________
41.
Urine and blood drug levels are best used by law enforcement authorities and the courts to _________ other
investigative and medical findings pertaining to an individual’s condition.
42.
A program to train police as _________ incorporates systematic and standardized methods for examining suspects to
determine whether they have taken one or more drugs.
APPLICATION AND CRITICAL THINKING
1.
Answer the following questions about driving risk associated with drinking and blood-alcohol concentrations:
a) Randy is just barely legally intoxicated. How much more likely is he to have an accident than someone who is
sober?
b) Marissa, who has been drinking, is fifteen times as likely to have an accident as her sober friend, Christine.
What is Marissa’s approximate blood-alcohol concentration?
c) After several drinks, Charles is ten times as likely to have an accident as a sober person. Is he more or less
intoxicated than James, whose blood alcohol level is 0.10?
d) Under the original blood-alcohol standards recommended by the National Highway Traffic Safety
Administration, a person considered just barely legally intoxicated was how much more likely to have an
accident than a sober individual?
2.
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Following are descriptions of four individuals who have been drinking. Rank them by blood-alcohol concentration,
from highest to lowest:
a) John, who weighs 200 pounds and has consumed eight 8-ounce drinks on a full stomach
b) Frank, who weighs 170 pounds and has consumed four 8-ounce drinks on an empty stomach
c) Gary, who weighs 240 pounds and has consumed six 8-ounce drinks on an empty stomach
d) Stephen, who weighs 180 pounds and has consumed six 8-ounce drinks on a full stomach
3.
Following are descriptions of four individuals who have been drinking. In which (if any) of the following countries
would each be considered legally drunk: the United States, Australia, and/or Sweden?
a) Bill, who weighs 150 pounds and has consumed three 8-ounce drinks on an empty stomach
b) Sally, who weighs 110 pounds and has consumed three 8-ounce drinks on a full stomach
c) Rich, who weighs 200 pounds and has consumed six 8-ounce drinks on an empty stomach
d) Carrie, who weighs 140 pounds and has consumed four 8-ounce drinks on a full stomach
4.
You are a forensic scientist who has been asked to test two blood samples. You know that one sample is suspected of
containing barbiturates and the other contains no drugs; however, you cannot tell the two samples apart. Describe how
you would use the concept of pH to determine which sample contains barbiturates. Explain your reasoning.
5.
You are investigating an arson scene and you find a corpse in the rubble, but you suspect that the victim did not die as
a result of the fire. Instead, you suspect that the victim was murdered earlier and that the blaze was intentionally started
to cover up the murder. How would you go about determining whether the victim died before the fire?
ENDNOTES
1.
In the United States, laws that define blood-alcohol levels almost exclusively use the unit percent weight per
volume —% w/v. Hence, 0.015 percent w/v is equivalent to 0.015 gram of alcohol per 100 milliliters of blood, or 15
milligrams of alcohol per 100 milliliters.
2.
R. B. Forney et al., “Alcohol Distribution in the Vascular System: Concentrations of Orally Administered Alcohol in
Blood from Various Points in the Vascular System and in Rebreathed Air During Absorption,” Quarterly Journal of
Studies on Alcohol 25 (1964): 205.
3.
G. A. Brown et al., “The Stability of Ethanol in Stored Blood,” Analytica Chemica Acta 66 (1973): 271.
4.
0.15 percent w/v is equivalent to 0.15 grams of alcohol per 100 milliliters of blood, or 150 milligrams per 100
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milliliters.
5.
384 U.S. 757 (1966).
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13 Trace Evidence I: Hairs and Fibers
© Bettmann/CORBIS All Rights Reserved
LEARNING OBJECTIVES
After studying this chapter, you should be able to:
• Recognize and understand the cuticle, cortex, and medulla areas of hair.
• List the three phases of hair growth.
• Appreciate the distinction between animal and human hairs.
• List hair features that are useful for microscopic comparisons of human hairs.
• Explain the proper collection of forensic hair evidence.
• Describe and understand the role of DNA typing in hair comparisons.
• Understand the differences between natural and manufactured fibers.
• List the properties of fibers that are most useful for forensic comparisons.
• Describe the proper collection of fiber evidence.
JEFFREY MACDONALD: FATAL VISION
The grisly murder scene that confronted police on February 17, 1970, is one that would not be wiped from memory.
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Summoned to the Fort Bragg residence of Captain Jeffrey MacDonald, a physician, police found the bludgeoned body
of MacDonald’s wife. She had been repeatedly knifed, and her face was smashed to a pulp. MacDonald’s two children,
ages 2 and 5, had been brutally and repeatedly knifed and battered to death.
Suspicion quickly fell on MacDonald. To the eyes of investigators, the murder scene had a staged appearance.
MacDonald described a frantic effort to subdue four intruders who had slashed at him with an ice pick. However, the
confrontation left MacDonald with minor wounds and no apparent defensive wounds on his arms. MacDonald then
described how he had covered his slashed wife with his blue pajama top. Interestingly, when the body was removed,
blue threads were observed under the body. In fact, blue threads matching the pajama top turned up throughout the
house—nineteen in one child’s bedroom, including one beneath her fingernail, and two in the other child’s bedroom.
Eighty-one blue fibers were recovered from the master bedroom, and two were located on a bloodstained piece of
wood outside the house.
Forensic examination showed that the forty-eight ice pick holes in the pajama top were smooth and cylindrical, a sign
that the top was stationary when it was slashed. Also, folding the pajama top demonstrated that the forty-eight holes
actually could have been made by twenty-one thrusts of an ice pick. This coincided with the number of wounds that
MacDonald’s wife sustained. As described in the book Fatal Vision , which chronicles the murder investigation, when
MacDonald was confronted with adulterous conduct, he replied, “You guys are more thorough than I thought.”
MacDonald is currently serving three consecutive life sentences.
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