Chain of Custody
The movement and location of physical evidence from the time it is obtained until the time it is presented in court.
Judges in bench trials and jurors in jury trials are obligated to decide cases on the evidence that is presented to them in court. Neither judges nor jurors may conduct their own investigations into the underlying facts of a given case. In fact, state and federal court rules prohibit judges and jurors from being swayed by, or even taking into consideration, extrajudicial evidence—that is, evidence that is not properly admitted into the record pursuant to the rules of evidence—in rendering their decisions.
Similarly, parties to civil and criminal litigation depend on judges and juries to impartially weigh the evidence, and only the evidence, that is properly admitted into the record. Every day, across the United States, litigants stake their reputations, livelihoods, bank accounts, homes, PERSONAL PROPERTY, and freedom on the premise that the outcome to their judicial proceedings will be one that is reached fairly and justly, according to the evidence.
Court-rendered judgments and jury verdicts that are based on tainted, unreliable, or compromised evidence would undermine the integrity of the entire legal system if such outcomes became commonplace. One way in which the law tries to ensure the integrity of evidence is by requiring proof of the chain of custody by the party who is seeking to introduce a particular piece of evidence.
Proof of a chain of custody is required when the evidence that is sought to be introduced at trial is not unique or where the relevance of the evidence depends on its analysis after seizure. A proper chain of custody requires three types of testimony: (1) testimony that a piece of evidence is what it purports to be (for example, a litigant's blood sample); (2) testimony of continuous possession by each individual who has had possession of the evidence from the time it is seized until the time it is presented in court; and (3) testimony by each person who has had possession that the particular piece of evidence remained in substantially the same condition from the moment one person took possession until the moment that person released the evidence into the custody of another (for example, testimony that the evidence was stored in a secure location where no one but the person in custody had access to it).
Proving chain of custody is necessary to "lay a foundation" for the evidence in question, by showing the absence of alteration, substitution, or change of condition. Specifically, foundation testimony for tangible evidence requires that exhibits be identified as being in substantially the same condition as they were at the time the evidence was seized, and that the exhibit has remained in that condition through an unbroken chain of custody. For example, suppose that in a prosecution for possession of illegal narcotics, police sergeant A recovers drugs from the defendant; A gives police officer B the drugs; B then gives the drugs to police scientist C, who conducts an analysis of the drugs; C gives the drugs to police detective D, who brings the drugs to court. The testimony of A, B, C, and D constitute a "chain of custody" for the drugs, and the prosecution would need to offer testimony by each person in the chain to establish both the condition and identification of the evidence, unless the defendant stipulated as to the chain of custody in order to save time.
Chain of custody need not be demonstrated for every piece of tangible evidence that is accepted into the trial court's record. Physical evidence that is readily identifiable by the witness might not need to be supported by chain-of-custody proof. For example, no chain-of-custody foundation is required for items that are imprinted with a serial number or inscribed with initials by an officer who collected the evidence. Similarly, items that are inherently distinctive or memorable (for example, a holdup note written in purple crayon) might be sufficiently unique and identifiable that they establish the integrity of the evidence.
Whether the requisite foundation has been laid to establish chain of custody for an exhibit is a matter of discretion on the part of the trial judge. Possibilities of misidentification and adulteration must be eliminated, not absolutely, but as a matter of reasonable probability. Where there is sufficient testimony that the evidence is what it purports to be, and that testimony is offered by each responsible person in the chain of custody, discrepancies as to accuracy or reliability of testimony regarding the chain of custody go to the weight of the evidence and not to its admissibility, meaning that the evidence would be admitted into the record for the judge or jury to evaluate in light of any conflicting testimony that the chain of custody somehow had been compromised. While the party who offers the evidence has the burden of demonstrating the chain of custody, the party against whom the evidence is offered must timely object to the evidence when it is first introduced at trial, or the party will waive any objections as to its integrity based on a compromised chain of custody.
Giannelli, Paul. 1996. "Chain of Custody." Criminal Law Bulletin 32.
–——. 1983. "Chain of Custody and the Handling of Real Evidence." American Criminal Law Review 20.