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Switching to 20 Core CODIS Loci and the Impact on SAKI Testing

NCJ Number
Amy Jeanguenat
Date Published
August 2018
2 pages
This training and technical assistance resource for grantees of the federal Sexual Assault Kit Initiative (SAKI) - which involves implementation of a model to reduce backlogs of untested sexual assault kits (SAKs) in local and state jurisdictions - provides information on and suggestions for responding to the switch to a DNA amplification kit that types a minimum of 20 core loci from the Combined DNA Index System (CODIS).
On January 1, 2017, laboratories participating in the national DNA Index System (NDIS) switched to a DNA amplification kit that types a minimum of 20 core loci from the CODIS to align with the FBI requirement that was enacted that same day. Expanding the CODIS core loci became imperative as CODIS continued to grow in size, so as to reduce the possibility of fictitious matches. Other benefits of expanding the core loci are also outlined in this paper. Regarding vendor response to this change, three main vendors dominate the U.S. market for amplification kit chemistry, and each designed kits to test, at a minimum, the 20 core loci; improve discrimination power; increase recovery of degraded and inhibited samples; and heighten sensitivity. Vendors also decided to include additional markers compatible with earlier versions of kits and/or adding in Y-STR markers, creating 24- to 27-locus kits. Some examples of the names of these locus kits are listed in this paper. This paper advises that collaboration with laboratory personnel is critical during this transition period. The laboratory can help in determining whether samples involved in CODIS hits that were processed with different kits would benefit from additional testing or explain when further testing is unwarranted or unnecessary. Profiles developed with the 13 core CODIS loci are valuable, and effort should be made to obtain the proper documentation for upload authorization.

Date Created: February 14, 2019