Chain of custody refers to official documentation of the complete sequence of activities connected with collection, custody, transfer, examination, and deposition of evidence used in legal proceedings.
The evidence can be a physical evidence such as drugs seized from a person, or a weapon used in a crime. It can also be some evidence in electronic or other forms such as video recording or some storage medium in computer.
The chain of custody must include detailed information on persons collecting and handling the evidence, timing of various actions by such persons, conditions under which the actions took place, and the precautions taken to prevent tempering with the evidence.
The purpose of chain of custody of evidence is to ensure and provide a proof that no unauthorised access or tampering with the evidence took place. Without such back up of chain of custody, no evidence is valid in a court of law.
For example if a glass tumbler containing fingerprints of a person obtained from the scene of crime is presented as evidence then the chain of custody will record details such as.
- Description of the evidence.
- How obtained the evidence, from where and when.
- When it was handed over to forensic lab for examination, and the identity of person receiving it.
- Nature and timing of analysis performed on it.
- Details of handover of evidence to the evidence clerk.
- Details of the place of storage by the evidence clerk.
- Details of any other persons accessing and examining the evidence while it is in the custody of the evidence clerk.