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17 Document Examination

LEARNING OBJECTIVES

After studying this chapter, you should be able to:

• Define questioned document.

• Know what common individual characteristics are associated with handwriting.

• List some important guidelines for collecting known writings for comparison to a questioned document.

• Recognize some of the class and individual characteristics of printers and photocopiers.

• List some of the techniques document examiners use to uncover alterations, erasures, obliterations, and

variations in pen inks.

THE UNABOMBER

In 1978, a parcel addressed to a Northwestern University professor exploded as it was being opened by a campus

security officer. This was the start of a series of bomb-containing packages that were sent typically to universities and

airlines. Considering the intended victims, the perpetrator was dubbed UN (university) A (airlines) BOM—hence, the

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Unabomber.

The explosives were usually housed in a pipe within a wooden box. The explosive ingredients generally were black

powder, smokeless powder, or an ammonium nitrate mix. The box was filled with metal objects to create a shrapnel

effect on explosion. The device typically had the initials “FC” punched into it.

The first Unabomber fatality came in 1985, when a computer store owner was killed after picking up a package left

outside his business. The Unabomber emerged again in 1993 after a six-year hiatus when he mailed bombs to two

university professors. Their injuries were not fatal, but his next two attacks did result in fatalities.

In 1995, the case took an unexpected turn when the Unabomber promised to end his mad spree if his 35,000-word

typewritten “Manifesto,” which he had sent to the New York Times and the Washington Post were published by these

newspapers. The manifesto turned out to be a long, rambling rant against technology, but it offered valuable clues that

broke the case. David Kaczynski realized that the manifesto’s writing style and the philosophy it espoused closely

resembled that of his brother, Ted. His suspicions were confirmed by linguistics experts who carefully pored over the

manifesto’s content. Ted Kaczynski was arrested in Montana in 1996. Inside his ramshackle cabin were writings

similar to the manifesto, three manual typewriters, and bomb-making materials. Forensic document examiners were

able to match the typewritten manifesto to one of the typewriters recovered from the cabin.

Document Examiner

Ordinarily, the work of the document examiner involves examining handwriting and typescript to ascertain the source

or authenticity of a questioned document. However, document examination is not restricted to a mere visual

comparison of words and letters. The document examiner must know how to use microscopy, photography, and even

such analytical methods as chromatography to uncover all efforts, both brazen and subtle, to change the content or

meaning of a document.

Alterations of documents through overwriting, erasures, or the more obvious crossing out of words must be recognized

and characterized as efforts to alter or obscure the original meaning of a document. The document examiner identifies

such efforts and recovers the original contents of the writing. An examiner may even reconstruct writing on charred or

burned papers, or uncover the meaning of indented writings found on a paper pad after the top sheet has been removed.

Any object that contains handwritten or typewritten markings whose source or authenticity is in doubt may be referred

to as a questioned document . This broad term may be applied to any of the written and printed materials we normally

encounter in our daily activities. Letters, checks, driver’s licenses, contracts, wills, voter registrations, passports,

petitions, and even lottery tickets are commonly examined in crime laboratories. However, we need not restrict our

examples to paper documents. Questioned documents may include writings or other markings found on walls,

windows, doors, or any other objects.

questioned document

Any document about which some issue has been raised or that is the subject of an investigation.

Document examiners possess no mystical powers or scientific formulas for identifying the authors of writings. They

apply knowledge gathered through years of training and experience to recognize and compare the individual

characteristics of questioned and known authentic writings. For this purpose, gathering documents of known

authorship or origin is critical to the outcome of the examination. Collecting known writings may entail considerable

time and effort and may be further hampered by uncooperative or missing witnesses. However, the uniqueness of

handwriting makes this type of physical evidence, like fingerprints, one of few definitive individual characteristics

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available to the investigator, a fact that certainly justifies an extensive investigative effort.

Handwriting Comparisons

Document experts continually testify that no two individuals write exactly alike. This is not to say that there cannot be

marked resemblances between two individuals’ handwritings because many factors make up the total character of a

person’s writing.

GENERAL STYLE

Perhaps the most obvious feature of handwriting to the layperson is its general style. As children, we all learn to write

by attempting to copy letters that match a standard form or style shown to us by our teachers. The style of writing

acquired by the learner is that which is fashionable for the particular time and locale. In the United States, for example,

the two most widely used systems of cursive writing are the Palmer method, first introduced in 1880, and the Zaner-

Bloser method, introduced in about 1895 (see Figure 17-1 ). To some extent, both of these systems are taught in nearly

all fifty states.

FIGURE 17-1 (top) An example of Zaner-Bloser handwriting; (bottom) an

example of Palmer handwriting.

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Courtesy Robert J. Phillips, Document Examiner, Audubon, NJ

The early stages of learning and practicing handwriting are characterized by a conscious effort by the student to copy

standard letter forms. Many pupils in a handwriting class tend at first to have writing styles that are similar to one

another, with minor differences attributable to skill in copying. However, as initial writing skills improve, a child

normally reaches the stage at which the nerve and motor responses associated with the act of writing become

subconscious. The individual’s writing now begins to take on innumerable habitual shapes and patterns that distinguish

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it from all others. The document examiner looks for these unique writing traits.

VARIATIONS IN HANDWRITING

The unconscious handwriting of two individuals can never be identical. Individual variations associated with

mechanical, physical, and mental functions make it extremely unlikely that all of these factors can be exactly

reproduced by any two people. Thus, variations are expected in angularity, slope, speed, pressure, letter and word

spacings, relative dimensions of letters, connections between letters, pen movement, writing skill, and finger dexterity.

Furthermore, many other factors besides pure handwriting characteristics should be considered. The arrangement of

the writing on the paper may be as distinctive as the writing itself. Margins, spacings, crowding, insertions, and

alignment are all results of personal habits. Spelling, punctuation, phraseology, and grammar can be personal and, if

so, combine to individualize the writer.

In a problem involving the authorship of handwriting, all characteristics of both the known and questioned documents

must be considered and compared. Dissimilarities between the two writings strongly indicate two writers, unless these

differences can logically be accounted for by the facts surrounding the preparation of the documents. Because any

single characteristic, even the most distinctive one, may be found in the handwriting of other individuals, no single

handwriting characteristic can, by itself, be taken as the basis for a positive comparison. The final conclusion of a

match must be based on a sufficient number of common characteristics between the known and questioned writings to

effectively preclude their having originated from two different sources.

What constitutes a sufficient number of personal characteristics? Here again, there are no hard-and-fast rules for

making such a determination. The expert examiner can make this judgment only in the context of each particular case.

CHALLENGES TO HANDWRITING COMPARISON

When the examiner receives a reasonable amount of known handwriting for comparison, sufficient evidence to

determine the source of a questioned document is usually easy to find. Frequently, however, circumstances prevent a

positive conclusion or permit only the expression of a qualified opinion. Such situations usually develop when an

insufficient number of known writings are available for comparison. Although nothing may be found that definitely

points to the questioned and known handwriting being of different origin, not enough personal characteristics may be

present in the known writings that are consistent with the questioned materials.

Difficulties may also arise when the examiner receives questioned writings containing only a few words, all

deliberately written in a crude, unnatural form or all very carefully written and thought out to disguise the writer’s

natural style—a situation usually encountered in threatening or obscene letters. It is extremely difficult to compare

handwriting that has been very carefully prepared to another document written with such little thought for structural

details that it contains only the subconscious writing habits of the writer. However, although one’s writing habits may

be relatively easy to change for a few words or sentences, maintaining such an effort grows more difficult with each

additional word.

When an adequate amount of writing is available, the attempt at total disguise may fail. This is illustrated by Clifford

Irving’s attempt to forge letters in the name of the late industrialist Howard Hughes in order to obtain lucrative

publishing contracts for Hughes’s life story. Figure 17-2 shows forged signatures of Howard Hughes along with

Clifford Irving’s known writings. By comparing these signatures, document examiner R. A. Cabbane of the US Postal

Inspection Service detected many examples of Irving’s personal characteristics in the forged signatures.

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FIGURE 17-2 Forged signatures of Howard Hughes and examples of

Clifford Irving’s writing.

For example, note the formation of the letter r in the word Howard on lines 1 and 3, compared with the composite on

line 6. Observe the manner in which the terminal stroke of the letter r tends to terminate with a little curve at the

baseline of Irving’s writing and the forgery. Notice the way the bridge of the w drops in line 1 and also in line 6. Also,

observe the similarity in the formation of the letter g as it appears on line 1 compared with the second signature on line

The document examiner must also be aware that writing habits may be altered beyond recognition by the influence of

drugs or alcohol. Under these circumstances, it may be impossible to obtain known writings of a suspect written under

conditions comparable to those at the time the questioned document was prepared.

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COLLECTION OF HANDWRITING EXEMPLARS

The collection of an adequate number of known writings, or exemplars , is critical for determining the outcome of a

comparison. Generally, known writings of the suspect furnished to the examiner should be as similar as possible to the

questioned document. This is especially true with respect to the writing implement and paper. Styles and habits may be

somewhat altered if a person switches from a pencil to a ballpoint pen or to a fountain pen. The way the paper is ruled,

or the fact that it is unruled, may also affect the handwriting of a person who has become particularly accustomed to

one type or the other. Known writings should also contain some of the words and combinations of letters present in the

questioned document.

exemplar

An authentic sample used for comparison purposes, such as a handwriting sample.

FIGURE 17-3 Examples of handwriting from the same individual over an

extended period of time.

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Courtesy Robert J. Phillips, Document Examiner, Audubon, NJ

The known writings must be adequate in number to show the examiner the range of natural variations in a suspect’s

writing characteristics. No two specimens of writing prepared by one person are ever identical in every detail.

Variation is an inherent part of natural writing. In fact, a signature forged by tracing an authentic signature can often be

detected even if the original and tracing coincide exactly because no one ever signs two signatures exactly alike (see

Figure 17-3 ).

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natural variations

Normal deviations found between repeated specimens of an individual’s handwriting.

Many sources are available to the investigator for establishing the authenticity of the writings of a suspect. An

important consideration in selecting sample writings is the age of the genuine document relative to the questioned one.

It is important to try to find standards that date closely to the questioned document. For most typical adults, basic

writing changes are comparatively slow. Therefore, material written within two or three years of the disputed writing is

usually satisfactory for comparison; as the time between the writing of the genuine and unknown specimens becomes

greater, the standard tends to become less representative.

Despite the many potential sources of handwriting exemplars, obtaining an adequate set of collected standards may be

difficult or impossible. In these situations, handwriting may have to be obtained from the suspect either voluntarily or

under court order. Ample case law supports the constitutionality of taking handwriting specimens. In Gilbert v.

California , the Supreme Court upheld the taking of handwriting exemplars before the appointment of counsel.

The

Court also reasoned that handwriting samples are identifying physical characteristics that lie outside the protection

privileges of the Fifth Amendment. Furthermore, in United States v. Mara , the Supreme Court ruled that taking a

handwriting sample did not constitute an unreasonable search and seizure of a person and hence did not violate Fourth

Amendment rights.

CASEFILES HITLER’S DIARIES

In 1981, a spectacular manuscript attributed to Adolf Hitler was disclosed by the brother of an East German general.

These documents included Hitler’s twenty-seven-volume diary and an unknown third volume of his autobiography,

Mein Kampf . The existence of these works was both culturally and politically significant to the millions who were

affected by World War II.

Authentication of the diaries was undertaken by two world-renowned experts, one Swiss and one American. Both

declared that the handwritten manuscripts were identical to the known samples of Adolf Hitler’s handwriting that they

were given. Bidding wars began for publishing rights, and a major national newspaper in the United States won with a

price near $4 million.

The publishing company that originally released the documents to the world market undertook its own investigation,

which ultimately revealed a clever but devious plot. The paper on which the diaries were written contained a whitener

that didn’t exist until 1954, long after Hitler committed suicide. The manuscript’s binding threads contained viscose

and polyester, neither of which was available until after World War ll. Further, the inks used in the manuscript were all

inconsistent with those in use during the year the pages were allegedly written.

Moreover, the exemplars sent to the Swiss and American experts as purportedly known examples of Hitler’s

handwriting were actually from the same source as the diaries. Thus, the experts were justified in proclaiming the

documents were authentic because they were written by the same hand—it just wasn’t Hitler’s. Chemical analysis of

the inks later determined that the “Hitler diaries” were in fact less than one year old—spectacular, but fake!

As opposed to nonrequested specimens (i.e., those written without the thought that they may someday be used in a

police investigation), requested writing samples may be consciously altered by the writer. However, the investigator

can take certain steps to minimize attempts at deception. The requirement of several pages of writing normally

provides enough material that is free of nervousness or attempts at deliberate disguise for a valid comparison. In

addition, writing from dictation yields exemplars that best represent the suspect’s subconscious style and

characteristics.

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Other steps that can be taken to minimize a conscious writing effort, as well as to ensure conditions approximating

those of the questioned writing, can be summarized as follows:

1. The writer should be allowed to write sitting comfortably at a desk or table and without distraction.

2. The suspect should not, under any conditions, be shown the questioned document or be told how to spell

certain words or what punctuation to use.

3. The suspect should be furnished a pen and paper similar to those used in the questioned document.

4. The dictated text should be the same as the contents of the questioned document, or at least should contain

many of the same words, phrases, and letter combinations found in the document. In handprinting cases, the

suspect must not be told whether to use uppercase (capital) or lowercase (small) lettering. If, after writing

several pages, the writer fails to use the desired type of lettering, he or she can then be instructed to include it.

Altogether, the text must be no shorter than a page.

5. Dictation of the text should take place at least three times. If the writer is trying to disguise the writing,

noticeable variations should appear among the three repetitions. Discovering this, the investigator must insist on

continued repetitive dictation of the text.

6. Signature exemplars can best be obtained when the suspect is required to combine other writings with a

signature. For example, instead of compiling a set of signatures alone, the writer might be asked to fill out

completely twenty to thirty separate checks or receipts, each of which includes a signature.

7. Before requested exemplars are taken from the suspect, a document examiner should be consulted and shown

the questioned specimens.

Quick Review

• Any object with handwriting or print whose source or authenticity is in doubt may be referred to as a

questioned document.

• Document examiners gather documents of known authorship or origin and compare them to the individual

characteristics of questioned writings.

• Collecting an adequate number of known writings is critical for determining the outcome of a handwriting

comparison. Known writing should contain some of the words and combinations of letters in the questioned

document.

• The unconscious handwriting of two individuals can never be identical. However, the writing style of an

individual may be altered beyond recognition by the influence of drugs or alcohol.

Typescript Comparisons

The document examiner analyzes not only handwritten documents but machine-created ones as well. Document-

creating machines include a wide variety of devices; some examples are computer printers, photocopiers, fax

machines, and typewriters.

PHOTOCOPIER, PRINTER, AND FAX EXAMINATION

With the emergence of digital technology, document examiners are confronted with a new array of machines capable

of creating documents subject to alteration or fraudulent use. Personal computers use daisy wheel, dot-matrix, ink-jet,

and laser printers. More and more, the document examiner encounters problems involving these machines, which often

produce typed copies that have only inconspicuous defects.

In the cases of photocopiers, fax machines, and computer printers, an examiner may need to identify the make and

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model of the machine that may have been used in printing a document. Alternatively, the examiner may need to

compare a questioned document with test samples printed from a suspect machine. Typically, the examiner generates

approximately ten samples through each machine to obtain a sufficient representation of a machine’s characteristics. A

side-by-side comparison is then made between the questioned document and the printed exemplars to compare

markings produced by the machine.

PHOTOCOPIERS

Transitory defect marks originating from random debris on the glass platen, inner cover, or mechanical portions of a

copier produce images. These images are often irregularly shaped and sometimes form distinctive patterns. Thus, they

become points of comparison as the document examiner attempts to link the document to suspect copiers. The gradual

change, shift, or duplication of these marks may help the examiner date the document.

FAX MACHINES

Fax machines print a header known as the transmitting terminal identifier (TTI) at the top of each fax page. For the

document examiner, the TTI is a very important point of comparison (see Figure 17-4 ). The header and the document’s

text should have different type styles. TTIs can be fraudulently prepared and placed in the appropriate position on a fax

copy. However, a microscopic examination of the TTI’s print quickly reveals significant characteristics that distinguish

it from a genuine TTI.

FIGURE 17-4 A fax page showing a transmitting terminal identifier

(TTI).

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Pearson Education PH Chet

In determining the fax machine’s model type, the examiner usually begins by analyzing the TTI type style. The fonts

of that line are determined by the sending machine. The number of characters, their style, and their position in the

header are best evaluated through a collection of TTI fonts organized into a useful database. One such database is

maintained by the American Society of Questioned Document Examiners.

COMPUTER PRINTERS

The determination of what model of computer printer has been used requires extensive analysis of the specific printer

technology and type of ink used. Visual and microscopic techniques help determine the technology and toner used.

Generally printers are categorized as impact and nonimpact printers by the mechanism of their toner application.

Nonimpact printers, such as ink-jet and laser printers, and impact printers, such as thermal and dot-matrix printers, all

have characteristic ways of printing documents. Character shapes, toner differentiation, and toner application methods

are easily determined with a low-power microscope and help the examiner narrow the possibilities of model type.

In analyzing computer printouts and faxes, examiners use the same approach for comparing the markings on a

questioned document to exemplar documents generated by a suspect machine. These markings include all possible

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transitory patterns arising from debris and other extraneous materials. When the suspect machine is not available, the

examiner may need to analyze the document’s class characteristics to identify the make and model of the machine. It is

important to identify the printing technology, the type of paper, the type of toner or ink used, the chemical composition

of the toner, and the type of toner-to-paper fusing method used in producing the document.

Examination of the toner usually involves microscopic analysis to characterize its surface morphology, followed by

identification of the inorganic and organic components of the toner. These results separate model types into categories

based on their mechanical and printing characteristics. Typically, document examiners access databases to help identify

the model type of machine used to prepare a questioned document. The resulting list of possibilities produced by the

database hopefully reduces the number of potential machines to a manageable number. Obviously, once a suspect

machine is identified, the examiner must perform a side-by-side comparison of questioned and exemplar printouts, as

already described.

TYPEWRITERS

Although typewriters are not used as widely as they were at one time, document examiners still analyze typescripts.

Examiners are most often asked the following two questions about typewriters: (1) Can the make and model of the

typewriter used to type the questioned document be identified? (2) Can a particular suspect typewriter be identified as

having prepared the questioned document?

FIGURE 17-5 A portion of a typewriting comparison points to the

conclusion that the same machine typed both specimens. Besides the

similarity in the design and size of type, note the light impression

consistently made by the letter M . Also, the letter E slants to the right,

almost touching D in the word USED in both specimens.

To answer the first question, the examiner must have access to a complete reference collection of past and present

typefaces used by typewriter manufacturers. The two most popular typeface sizes are pica (with ten letters to the inch)

and elite (with twelve letters to the inch). Although a dozen manufacturers may use a pica or an elite typeface, many of

these are distinguishable when the individual type character’s style, shape, and size are compared.

As with any mechanical device, use of a typewriter will result in wear and damage to the machine’s moving parts.

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These changes occur both randomly and irregularly, thereby imparting individual characteristics to the typewriter.

Variations in vertical and horizontal alignment (i.e., characters are too high or low or too far to the left or right of their

correct position) and perpendicular misalignment of characters (i.e., characters leaning to the left or to the right), as

well as defects in each typeface, are valuable for proving the identity of a typewriter (see Figure 17-5 ).

Associating a particular typewriter with a typewritten document requires comparing the questioned document to

exemplars prepared from the suspect typewriter. As with handwriting, collection of proper standards is the foundation

of such comparisons. In this respect, it is best if the document examiner has access to the questioned typewriter, and

thus is able to prepare an adequate number of exemplars and examine the machine’s typefaces. If the investigator must

prepare standards from the questioned machine, a minimum of one full, word-for-word copy of the questioned

typewriting must be created.

Another area of investigation relates to the ribbon. An examination of the type impressions left on a ribbon may reveal

the portion of the ribbon on which a particular text was typed.

When the suspect typewriter is not available for examination, the investigator must gather known writings that have

been typed on the suspect machine. Ideally, material should be selected that contains many of the same combinations

of letters and words found on the questioned document. The individual defects that characterize a typewriter develop

and change as the machine is used; some may have changed between the preparation of the questioned and standard

material. Hence, if many specimens are available, those prepared near the time of the disputed document should be

collected.

Quick Review

• The examiner compares the individual type character’s style, shape, and size to a complete reference collection

of past and present typefaces.

• Use of a printing device results in wear and damage to the machine’s moving parts in a way that is both

random and irregular, thereby imparting individual characteristics to it.

• Transitory defect marks originating from random debris on the glass platen, inner cover, or mechanical

portions of a copier produce irregularly shaped images that may serve as points of comparison.

• A TTI, or transmitting terminal identifier, is a header at the top of each page of a fax document. It is useful in

document comparison because it serves as a way to distinguish between a real and a fraudulently prepared fax

document.

• Variations in vertical and horizontal alignment and perpendicular misalignment of characters, as well as defects

in each typeface, are valuable for proving the identity of a typewriter.

Alterations, Erasures, and Obliterations

Documents are often altered or changed after preparation, to hide their original intent or to perpetrate a forgery.

Documents can be changed in several ways, and for each way, the application of a special discovery technique is

necessary.

One of the most common ways to alter a document is to try to erase parts of it, using an India rubber eraser, sandpaper,

a razor blade, or a knife to remove writing or type by abrading or scratching the paper’s surface. All such attempts at

erasure disturb the upper fibers of the paper. These changes are apparent when the suspect area is examined under a

microscope using direct light or by allowing the light to strike the paper obliquely from one side (i.e., side lighting).

Although microscopy may reveal whether an erasure has been made, it does not necessarily indicate the original

letters or words present. Sometimes so much of the paper has been removed that identifying the original contents is

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impossible.

erasure

The removal of writing, typewriting, or printing from a document, normally accomplished either by chemical means or

by means of an abrasive instrument.

In addition to abrading the paper, the perpetrator may also obliterate words with chemicals. In this case, strong

oxidizing agents are placed over the ink, producing a colorless reaction product. Although such an attempt may not be

noticeable to the naked eye, examination under the microscope reveals discoloration on the treated area of the paper.

Sometimes examination of the document under ultraviolet or infrared lighting reveals the chemically treated portion of

the paper. Interestingly, examination of documents under ultraviolet light may also reveal fluorescent ink markings that

go unnoticed in room light, as seen in Figure 17-6 .

FIGURE 17-6 (a) A $20 bill as it appears under room light. (b) The bill

illuminated with ultraviolet light reveals ink writing.

Courtesy Sirchie Fingerprint Laboratories, Inc., Youngsville, NC, www.sirchie.com

Some inks, when exposed to blue-green light, absorb the radiation and reradiate infrared light. This phenomenon is

known as infrared luminescence . Thus, alteration of a document with ink differing from the original can sometimes

be detected by illuminating the document with blue-green light and using infrared-sensitive film to record the light

emanating from the document’s surface. In this fashion, any differences in the luminescent properties of the inks are

observed (see Figure 17-7 ). Infrared luminescence has also revealed writing that has been erased. Such writings may

be recorded by invisible residues of the original ink that remain embedded in the paper even after an erasure.

FIGURE 17-7 (a) Part of a check stolen from a government agency as it

appears to the naked eye. (b) An infrared luminescence photograph was

prepared of the amount figures at a magnification of 10×. This clearly

shows that the number 2 was added with a different ink. The accused

pleaded guilty.

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Another important application of infrared photography arises from the observation that inks differ in their ability to

absorb infrared light. Thus, illuminating a document with infrared light and recording the light reflected off the

document’s surface with infrared-sensitive film enables the examiner to differentiate inks of a dissimilar chemical

composition (see Figure 17-8 ).

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FIGURE 17-8 (a) This photograph, taken under normal illumination,

shows the owner of an American Express check to be “Freda C. Brightly

Jones.” Actually, this signature was altered. The check initially bore the

signature “Fred C. Brightly Jr.” (b) This photograph, taken under

infrared illumination using infrared-sensitive film, clearly shows that the

check was altered by adding a to Fred and ones to Jr . The ink used to

make these changes is distinguishable because it absorbs infrared light,

whereas the original ink does not.

Intentional obliteration of writing by overwriting or crossing out is seldom used for fraudulent purposes because of its

obviousness. Nevertheless, such cases may be encountered in all types of documents. Success at permanently hiding

the original writing depends on the material used to cover the writing. If it is done with the same ink that was used to

write the original material, recovery will be difficult if not impossible. However, if the two inks are of a different

chemical composition, photography with infrared-sensitive film may reveal the original writing. Infrared radiation may

pass through the upper layer of writing while being absorbed by the underlying area (see Figure 17-9 ).

infrared luminescence

A property exhibited by some dyes, meaning that they emit infrared light when exposed to blue-green light.

obliteration

Blotting out or smearing over writing or printing to make the original unreadable.

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FIGURE 17-9 (a) A photograph showing an area of a document that has

been blacked out with a heavy layer of ink overwriting. (b) In this

photograph, the covering ink has been penetrated by infrared

photography to reveal the original writing.

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Close examination of a questioned document sometimes reveals crossing strokes or strokes across folds in the paper

that are not in a sequence that is consistent with the natural preparation of the document. Again, these differences can

be shown by microscopic or photographic scrutiny.

Infrared photography sometimes reveals the contents of a document that has been accidentally or purposely charred in

a fire. Another way to decipher charred documents involves reflecting light off the paper’s surface at different angles

in order to contrast the writing against the charred background (see Figure 17-10 ).

charred document

Any document that has become darkened and brittle through exposure to fire or excessive heat.

FIGURE 17-10 Decipherment of charred papers seized in the raid of a

suspected bookmaking establishment. The charred documents were

photographed with reflected light.

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Digital image processing is the method by which the visual quality of digital pictures is improved or enhanced.

Digitizing is the process by which the image is stored in memory. This is commonly done by scanning an image with a

flatbed scanner or a digital camera and converting the image by computer into an array of digital intensity values

called pixels , or picture elements. Once the image has been digitized, an image-editing program such as Adobe

Photoshop is used to adjust the image. The image may be enhanced through lightening, darkening, and color and

contrast controls. Examples of how the technology is applied to forensic document examination are shown in Figures

17-11 and 17-12 .

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FIGURE 17-11 This composite demonstrates the various changes that can

be applied to a digitized image to reveal information that has been

obscured. Using photo-editing software (in this case, Adobe Photoshop),

the original was duplicated and pasted as a second layer. Colors were

changed in selected areas of the image using the “screen” and “exclusion”

options. “Replace color” allows the user to choose a specific color or range

of colors and lighten, darken, or change the hue of the colors selected.

“Level” and “curves” tools can adjust the lightest and darkest color

ranges and optimize contrast, highlights, and shadow detail of the image

for additional clarity.

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FIGURE 17-12 (a) Receipts are used in investigations to establish a

victim’s whereabouts, provide suspects with alibis, and substantiate a host

of personal conduct. Unfortunately, because of wear, age, or poor printing

by the register, receipts are often unreadable. This can be corrected using

photo-editing software. In this example, the original toll receipt was

scanned at the highest color resolution, which allows more than 17 million

colors to be reproduced. The image was then manipulated, revealing the

printed details, by adjusting the lightest and darkest levels and the color

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content of the image. (b) Invoices may contain details about a transaction

that are important to an investigation. The copy that ships with the

merchandise may have that information blocked out. This information

may be recovered using digital imaging. The figure on the left shows the

original shipping ticket. The figure on the right shows the information

revealed after replacing the color of the blocking pattern.

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