AUTHENTICATION OF EVIDENCE: THE CHAIN OF CUSTODY
Virtually all real evidence is subject to authentication. There must be a showing that the evidence is in the same condition from the moment it has been seized at the crime scene until it is used in court. It must have “sponsors” who can identify it and follow its trail. The only exception to rigorous authentication of real evidence is when it has some unique characteristic that makes it differentiable from all other objects. This might include a weapon with a unique serial number that has been noted by a police officer when the weapon was first seized. Even in this case, the evidence must have a sponsor. The most commonly accepted method for authentication of evidence is the chain of custody. The chain of custody is both a process and a document that memorializes the transfer of evidence from the custody of one person to another. The process of authentication starts at the crime scene or anywhere where evidence is seized. Each item of evidence is given a unique identifier. Each piece of evidence is packaged separately in a tamper-evident container and sealed. The official who packages the evidence affixes a signature or initials and the date to the evidence container. Every time someone, such as a forensic scientist, opens the container to examine the evidence, it must be done so as to not disturb the already affixed seals. The evidence must be resealed and labeled with unique identifiers so it can be easily seen who opened it. The evidence is also accompanied by a chain of custody form as shown in Figure 1. This is a document that contains a description of the evidence and a place for the signatures of everyone who handles the evidence. That person signs for the evidence when it is received and then signs it over to the next person. Each sig nature is accompanied by the date and time. This way, one can tell who had custody of the evidence at any time and that person can be called to testify what condition the evidence was in, what was done to it, and how it was stored. The chain of custody in Figure 1 is imprinted on a tamper-evident evidence bag. A substantial break in the chain of custody, either the process or the documentation, can result in the evidence being excluded from admission to court. In such cases, the opponent must show that the break in the chain could have reasonably resulted in the evidence being adulterated or otherwise tampered with. This used to be a problem in hospitals and clinics where sexual assault victims were taken after the incident. The main concern of health care professionals is, of course, the health and welfare of the patient. As a result, important physical evidence was often left unattended and not properly packaged. Often, it was not admissible in court owing to the faulty chain of custody. In recent years, forensic science laboratories have developed and implemented a system of “rape kits” that contain proper packaging and chain of custody forms for this evidence. The result has been far fewer incidents of exclusion of evidence owing to chain of custody problems.
FIGURE 1 Chain of custody form. The form is on the front of a secure evidence package. As the evidence moves through the law enforcement, forensic science, and judicial system, anyone who has custody of the evidence must sign for it. This package is convenient because it provides a secure environment for the evidence as well as the chain of custody form.
