Maintaining chain of custody is one of the most important elements for making sure evidence stays legitimate.

Maintaining chain of custody is one of the most important elements for making sure evidence stays legitimate. Normally, the chain begins, and is recorded, once the evidence is discovered by someone in the legal system (eg, police, prosecutor, etc). What about chain of custody before someone from the legal system discovers the evidence? If the evidence passes through several hands first, does that invalidate the chain of custody?