Understanding the concept of a chain of custody is always critical to the use of evidence in a legal proceeding. As an expert witness, you do not always form a part of the legal ‘chain'. sometimes, you are given access to evidence in a secure facility and some one else is responsible for having obtained it and signed for the responsibility of the evidence. Depending on your particular discipline, you may in fact be given the original evidence itself. You must know how to properly handle it!
sometimes, your inspections of equipment, devices, or machinery will lead you to evidence that the police have seized as part of their investigation. They may require that you run your tests or make your observations in the police lockup, which is a location for holding evidence to be used in a criminal proceeding. You may occasionally be given temporary custody of evidence from the opposing side. When you receive admitted evidence, which has been given exhibit numbers by the authorities, you must maintain what is called a chain of custody.
Treat a chain of custody as a paper trail for the location of any piece of evidence in a legal matter. The paper trail shows where the evidence was and is, moment by moment, and assures everyone that it is the same evidence that was originally seized.
The chain of custody must be maintained from the moment the authorities first seize the evidence, until the final moment when it may be shown and referred to in a trial. Paper records must document changes in the custodianship of evidence: who transferred possession of the item, who accepted possession, the date of the transfer, the method of transfer, and additional data to identify the evidence precisely. sometimes, witness signatures are also required.
If the evidence is lost or destroyed while in your possession, you could be held legally and financially accountable. Be careful.