Chain of Custody refers to the logical sequence that records the sequence of custody, control, transfer, analysis and disposition of physical or electronic evidence in legal cases. Each step in the chain is essential as if broke, the evidence may be rendered inadmissible.
- Chain of custody refers to the probability of data provided as originally acquired and has not been changed before admission into evidence.
- In legal terms, it’s a chronological documentation/paper trail that records a proper sequence of custody, control, analysis, and disposition of electronic or physical evidence.
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Chain of custody refers to the documentation that establishes a record of the control, transfer, and disposition of evidence in a criminal case. If law enforcement does not do it correctly, chain of custody can be successfully challenged in a criminal case.
When deciding whether a defendant is guilty, judges and juries evaluate cases based on the evidence presented in court. They are not permitted to conduct their own investigations. Allowing judges or juries to base their decisions on evidence that is tainted, unreliable, or has been tampered with would undermine the integrity of the judicial system.
Chain of custody issues are particularly important in cases involving drugs, guns, or samples that have been tested for the presence of drugs or alcohol to prove intoxication. To prove chain of custody, prosecutors must present documentary and testimonial evidence to establish that the item presented at trial is the same item that was in the possession or taken from the defendant.
In a typical case, a police officer will collect evidence at the crime scene and give it to a forensics technician. The technician analyzes the evidence, for example, by testing a blood sample for the presence of alcohol or other intoxicating drugs, collecting fingerprints, or verifying that a substance collected at the scene is, in fact, an illegal drug. The forensic technician must document any tests that were performed on the evidence. When he has finished testing the evidence, he turns it over to an evidence clerk, who stores the evidence until it is needed for another test or to be presented at trial.
A defendant can challenge the chain of custody of a piece of evidence by questioning whether the evidence presented at trial is the same evidence as what was collected at the scene of the crime.
If there are any discrepancies in the chain of custody and law enforcement cannot prove who had the evidence at a particular time, the chain of custody is broken and the defendant can ask to have the evidence declared inadmissible so that it cannot be used to try to convict the defendant.
To prove chain of custody, prosecutors must present evidence that proves: (1) the evidence is what the prosecutor claims it is (e.g. that the white power is, in fact, cocaine, or that the blood sample actually came from the defendant); (2) continuous possession of the evidence from the time it was seized until it was presented in court; and (3) that the evidence remained in substantially the same condition from the time each time it was transferred.
The chain of custody can be broken if a custody form is labeled incorrectly, if a transfer of evidence takes an unreasonable amount of time, or if there is reason to believe the evidence was tampered with.
Even if there is sufficient testimony that evidence is what it purports to be and testimony has been offered to prove the chain of custody, discrepancies as to chain of custody can still be challenged and a judge or jury can use those discrepancies in assessing the weight and credibility of evidence after it has been admitted.