Seminar Details

Seminar Details


Feb 5

3:30 pm

The Strength of Evidence Found by Searching a Database

Chris Triggs


University of Auckland, New Zealand

The United Kingdom Home Office holds approximately 1 million DNA profiles in its database of known offenders. Suppose that a partial DNA profile is recovered from the scene of a crime. The probability of drawing this profile from a randomly selected individual in England and Wales is estimated to be 1/1,000,000. The crime scene profile is compared with each profile in the offender database and is found to match the profile of one person, S. S was not in custody at the time the crime took place, but no other evidence linking S to the scene of the crime is found.

Does the match probability of 1/1,000,000 constitute strong evidence against S, or, since 1,000,000 profiles were searched to find one matching the crime scene, provide no evidence at all? Opinion in the forensic science community is strongly divided between these two conclusions. In the United States the Second Report to the NRC on the Evaluation of DNA Evidence favoured the second alternative. In this talk I will review the background of the "database problem" and consider some recent contributions to the debate.