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Chain of Custody

Definition

The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes the hash value of the original media at acquisition, the identity and credentials of each handler, and the integrity checks applied at each transfer. Courts use the chain of custody to assess whether evidence could have been altered after seizure.

Field
Evidence management
Purpose
Prove evidence integrity
Recorded on
Chain-of-custody form / custody log
Matters when
Admissibility is challenged

Common questions

What is the chain of custody in forensics?+

It is the documented, unbroken record of everyone who handled a piece of evidence, along with when and how each transfer happened, from collection at the scene to presentation in court. The record exists to show the item was not altered, swapped or contaminated along the way.

Why is the chain of custody important?+

If the chain is broken, the opposing side can argue the evidence may have been tampered with or mixed up, and a court may reduce its weight or rule it inadmissible. An intact chain is what lets a lab result be trusted as belonging to the right case.

What happens if the chain of custody is broken?+

A gap does not automatically discard the evidence, but it gives grounds to challenge its reliability. A court weighs how large the gap is and whether tampering was plausible before deciding how much the evidence should count.

Related terms

Write Blocker
A hardware or software device interposed between a digital storage medium and the forensic workstation that prevents any write commands from reaching...
Hash Value
A fixed-length digital fingerprint produced by running a file through a cryptographic algorithm such as SHA-256 or MD5. Identical files produce identical...
Expert Witness
A person whose specialised knowledge is accepted by a court and who gives opinion evidence, not just factual evidence. Forensic auditors frequently...
Admissibility
Whether a piece of evidence is permitted to be placed before the fact-finder at all. Admissibility is a threshold question, decided by...
Authentication
The process of establishing that a document is what it purports to be. Under the US FRE Rule 901, the proponent must...
Daubert Standard
The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
Forensic Image
A bit-for-bit verified copy of a storage medium, created using a write-blocker to prevent modification of the original. The copy is verified...
Legal Hold
A directive from legal counsel instructing relevant people within an organisation to preserve documents, data, and physical items that may be relevant...
Mutual Legal Assistance Treaty (MLAT)
A bilateral or multilateral treaty under which signatory states agree to assist each other in gathering evidence for criminal investigations. MLATs define...
Reference Sample
A biological sample collected from a known individual (victim, suspect, or elimination source) for comparison against scene stains. Typically a buccal swab...
Tamper-Evident Seal
A physical barrier (tape, sticker, wax) applied to packaging that shows visible damage if the package has been opened after sealing. Courts...
Alternate Light Source (ALS)
A device emitting light at selected wavelengths (typically 415 to 535 nm) used to detect biological fluids that fluoresce or absorb light...

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