When offering physical evidence — such as drugs, blood samples, weapons, or electronic devices — the proponent must establish that the item is in substantially the same condition as when it was collected and has not been tampered with. This is accomplished by calling witnesses who handled the evidence at each stage to testify about their receipt, handling, and transfer of the item. The chain need not be perfect; minor gaps go to the weight rather than the admissibility of the evidence. However, significant unexplained gaps may provide grounds for exclusion. Defense counsel frequently attacks chain of custody in cases involving controlled substances, DNA evidence, and digital forensics.
Attorney: "Detective Ruiz, after you collected the firearm from the scene, what did you do with it?" Witness: "I placed it in a sealed evidence bag, labeled it with the case number and my initials, and transported it to the evidence locker at the precinct." Attorney: "And who next accessed the firearm?" Witness: "The forensics technician, Ms. Park, who signed it out on March 12th."
Opposing Counsel: "Your Honor, the prosecution cannot account for a 72-hour gap during which the blood sample sat in an unsecured refrigerator. The chain of custody is broken, and the evidence should be excluded."
Judge: "While there is a gap in the documentation, the evidence bag remained sealed and initialed. The gap goes to weight, not admissibility. The exhibit is admitted."
Students often believe that any gap in the chain of custody renders evidence inadmissible. In reality, the proponent need only show a reasonable probability that the evidence was not altered. Minor gaps affect the weight the jury gives the evidence, not its admissibility.
Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009)
Held that forensic laboratory certificates of analysis are testimonial statements subject to the Confrontation Clause, requiring live testimony from the analyst who performed the testing rather than admission through a certificate alone.
United States v. Lott, 114 F.3d 1183 (11th Cir. 1996)
Held that chain of custody is established by showing with reasonable certainty that the evidence was not altered, and that the government is not required to eliminate every possibility of tampering.
Does the chain of custody need to be perfect for evidence to be admitted?
No, the chain of custody does not need to be perfect. The proponent must show a reasonable probability that the evidence has not been altered or tampered with. Minor gaps or procedural irregularities go to the weight of the evidence (for the jury to consider) rather than its admissibility.
Who has the burden of establishing chain of custody?
The proponent of the evidence (the party seeking to admit it) bears the burden of establishing the chain of custody. This typically requires calling witnesses who handled the evidence at each stage to testify about their receipt, storage, and transfer of the item.
How is chain of custody established for digital evidence?
For digital evidence, chain of custody is established through forensic imaging protocols, hash value verification (MD5 or SHA-256), write-blocking technology, detailed documentation of acquisition and analysis steps, and testimony from the forensic examiner. The goal is to demonstrate the digital evidence has not been altered since collection.
Authentication is the process of proving that an item of evidence is what it purports to be. The pro...
Foundation refers to the preliminary showing that must be made before evidence is admitted. It estab...
Spoliation is the intentional, reckless, or negligent destruction, alteration, or concealment of evi...
Circumstantial evidence is evidence that requires an inference to connect it to a conclusion of fact...
