Maintaining a "Chain of Custody" of a blood alcohol test is critical in a DUI case. I saw the importance of maintaining a chain of custody on a recent visit to the Rocky Mountain Lab. What is the chain of custody? The general rule is that the tangible evidence may be properly introduced either when identified by a witness or by the presentation of an unbroken chain of custody. The purpose of the chain of custody is to demonstrate that there has been no tampering, loss, substitution or mistake with respect to the evidence.
Absent proof of the chain of custody, evidence should not be admitted into evidence unless both identity and integrity can be demonstrated by other appropriate means. With the increased use of blood tests and search warrants for blood in Tennessee, making sure the chain of custody is valid is critical.