Originals should be obtained, whenever possible. The investigator should document the recovery of each piece of evidence, noting the date, time, location, and by whom the item was recovered. The investigators may wish to create copies of the document for the working file, or for a business necessity. The investigators must maintain the chain of custody of any evidence that comes into their possession. A break in the chain of custody may result in the item or document being inadmissible at trial.
Chain of custody assures both the defense and prosecution of the evidence's integrity.
To maintain a chain of custody, the evidence must be stored in a secure location. When evidence is transferred from one person to another, the transfer must be documented. Evidence sent to a crime lab, document examiner, or police must be accounted for as well. The simplest way to do this is to create an evidence log that lists each item by number and description. Then any transfer is noted, by the evidence custodian, maintaining the item's chain of custody.