Partial Matches

Overview

A partial match occurs when a Combined DNA Index System (CODIS) search is conducted and the results clearly show that the offender profile is not the source of the crime scene profile (also referred to as a forensic profile), but the possibility does exist that a close biological relative of the offender might be the source of the crime scene profile.¹ CODIS searches can be conducted using various stringency modes:

• A high stringency search would only ‘hit’ on an offender sample when the DNA profiles are identical
• Moderate stringency searches include situations where one DNA profile is homozygous at a locus and the other is heterozygous with one of the two alleles being the same as the homozygous allele

¹ Scientific Working Group on DNA Analysis Methods Ad Hoc Committee on Partial Matches: SWGDAM Recommendations to the FBI Director on the “Interim Plan for the Release of Information in the Event of a ‘Partial Match’ at NDIS”, Forensic Science Communications October 2009, Volume 11, Number 4.