Uncertainty in the Number of Contributors in the Proposed New CODIS Set

• NCJ Number: 250064
• Author(s): M. D. Coble, J. A. Bright
• Date Published: November 2015
• Length: 5 pages
• Agencies: NIJ-Sponsored
• Award: Population Genetic Issues for Forensic DNA Profiles

Annotation

This study examined the probability of a mixed DNA profile appearing as having originated from a fewer number of contributors for the African American, Asian, Caucasian and Hispanic US populations, using a range of locus configurations from the proposed new CODIS set.

Abstract

The probability that multiple contributors are detected within a forensic DNA profile improves as more highly polymorphic loci are analysed. The assignment of the correct number of contributors to a profile is important when interpreting the DNA profiles. These theoretical calculations were based on allele frequencies only and ignored peak heights. This analysis shows that the probability of a higher order mixture (five or six contributors) appearing as having originated from one less individual is high. This probability decreases as the number of loci tested increases. (Publisher abstract modified)