Chain of custody

Definition: Documentation of the location of physical evidence from the time it is collected until the time it is introduced at trial.

Significance: The establishment of chain of custody is important for all physical evidence collected in criminal investigations, but it is particularly crucial when items of evidence might become confused with other evidence or when there is a possibility that someone could have tampered with the evidence.

In criminal investigations, the identification of an object as one found at a certain place involves the establishment of a proper chain of custody, or paper trail. Each piece of physical evidence must be authenticated or identified by a witness or through other means.

Authentication

Authentication involves proof that the evidence is what it purports to be. Rule 901 of the Federal Rules of Evidence sets out methods of authenticating or identifying evidence. According to the rule, authentication or identification may be established by any of the following means: testimony of a witness with knowledge that a matter is what it is claimed to be, a nonexpert opinion as to the genuineness of handwriting based on familiarity, comparison by the trier of fact (jury) or expert witness with specimens that have been authenticated, distinctive characteristics, voice identification, telephone conversations showing that a call was made to a certain number and the identification of the person who answered the phone individually or on behalf of a business, ancient document or data compilation in existence twenty years or more at the time it is offered, evidence describing a process or system used to produce a particular result, or a method provided by act of Congress or by other rules pursuant to statutory authority.

Proper Chain of Custody

The first clause of Rule 901 addresses proper chain of custody. A weapon found next to a victim and then taken by the police and put into a bag that is sealed and marked with identification can later be identified by an officer on the stand at trial as the one found next to the victim. If more than one person had access to the bag, however, the role of each must be accounted for to ensure that the evidence is truly the object it is claimed to be. Similarly, when a powder is put into an evidence bag that is then sealed and checked in to the evidence room, the bag may later be checked out and sent to a laboratory for analysis of the contents. The laboratory technician has the responsibility of keeping track of the substance while testing it. The technician can then take the stand and testify about the identity of the substance.

It should be noted that minor gaps in the chain of custody are permissible and do not destroy the chain of custody. The evidence can be considered by the jury, which will determine its reliability and its probative value, if any, given the missing links in the chain. If, however, the evidence is not what the proponent claims it to be because of tampering in the chain of custody, the judge may prevent the jury from seeing or considering the evidence.

Chain of Custody in Court

It is important that law-enforcement personnel document the seizure, custody, control, transfer, analysis, and disposition of physical and electronic evidence. Because evidence can be used in court to convict persons of crimes, it must be handled carefully to avoid later allegations of tampering or misconduct that can compromise cases. Establishing a chain of custody is especially significant when the evidence takes the form of fungible goods—that is, goods that can easily be substituted for other items in the same category. This applies to illegal drugs seized by law enforcement.

An identifiable person must always have custody of the evidence. Therefore, when a police officer or detective takes charge of a piece of evidence, the officer or detective must document the item and give it to an evidence clerk for secure storage. This transaction and every succeeding transaction affecting that evidence, from its collection to its appearance in court, should be completely documented so that the evidence can withstand any challenges to its authenticity. Properly detailed documentation includes the conditions under which the evidence was gathered, the identities of all those who handled the evidence and how long they had it in their possession, the security conditions that existed during handling and storing of the evidence, and the manners in which the evidence was transferred to subsequent custodians.

In the case of the recovery of a bloody weapon at a murder scene, for example, every transfer of the weapon from person to person must be documented, from the time the weapon is picked up at the scene to the time it is presented in court. Law-enforcement personnel must be able to prove that only persons with legitimate reasons to inspect, test, or otherwise examine the weapon have had access to it. In cases involving chemical sampling, proper chain of custody ensures maintenance of the condition of samples by providing documentation of their control, transfer, and analysis.

Bibliography

Broun, Kenneth S., ed. McCormick on Evidence. 6th ed. St. Paul, Minn.: Thomson/West, 2006.

Mauet, Thomas A. Trial Techniques, 8th ed, Wolters Kluwer Law and Business, 2010.

Rothstein, Paul F., Myrna S. Raeder, and David Crump. Evidence in a Nutshell. 5th ed. St. Paul, Minn.: West, 2007.

Pfefferli, Peter. Forensic Evidence Field Guide: A Collection of Best Practices. Academic Press, 2015. eBook Collection (EBSCOhost), search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=942215&site=ehost-live. Accessed 30 Dec. 2016.

Stopp, Margaret T. Evidence Law in the Trial Process. Albany, N.Y.: West/Delmar, 1999.