"Chain of custody" (COC) refers to the document or paper trail showing the seizure, custody, control, and transfer of physical evidence. Evidence item COC documentation should include the identity of all evidence handlers, duration of evidence custody, and the manner in which evidence is transferred each time such a transfer occurs.
An identifiable person must always have the physical custody of a piece of evidence. In practice, this means that an officer or crime scene personnel will take charge of a piece of evidence at the crime scene, document its collection, and ultimately hand it over to an evidence clerk for storage in a secure place. These transactions, and every succeeding transaction occurring between the collection of the evidence and its appearance in court, should be completely documented in order to withstand legal challenges to the authenticity of the evidence.