Overview

A partial match occurs when a CODIS search is conducted and an exact match is not displayed between the offender profile and the crime scene profile. These results must be evaluated to determine if the offender may be a source of a mixed donor or low level DNA profile, or if the offender profile is not a contributor to the crime scene profile. The evaluation may then determine there is a possibility that a close biological relative of the suspect might be the source of the crime scene profile.1 This scenario may arise because 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

A partial match should not be confused with familail searching which is discussed later in this module.

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.

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