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Developing criteria and data to determine best options for expanding the core CODIS loci
Jianye Ge1, Arthur Eisenberg, Bruce Budowle
1Institute of Applied Genetics, Department of Forensic and Investigative Genetics, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA. bruce.budowle@unthsc.edu.
Investigative Genetics
|January 10, 2012
Summary
The US Federal Bureau of Investigation (FBI) evaluated new Combined DNA Index System (CODIS) core loci for forensic DNA databases. Expanded sets of short tandem repeat (STR) loci improve kinship analysis and mixture deconvolution, supporting casework needs.
Area of Science:
- Forensic Genetics
- Molecular Biology
- Population Genetics
Background:
- The U.S. Federal Bureau of Investigation's (FBI) Combined DNA Index System (CODIS) Core Loci Working Group proposed an updated set of short tandem repeat (STR) loci.
- The proposed set includes 20 STR loci and the Amelogenin marker, expanding upon the original CODIS core set.
Purpose of the Study:
- To evaluate the performance of current and proposed CODIS core loci sets.
- To provide guidance for selecting optimal core loci for forensic DNA databases.
- To assess suitability for single-source profiles, mixture deconvolution, kinship analysis, and international data sharing.
Main Methods:
- Comparative analysis of adventitious hit rates for current and proposed CODIS core loci sets.
- Evaluation of informativeness metrics such as match probability and average kinship index (AKI).
- Assessment of locus performance with challenging forensic samples, including mixtures and kinship cases.
Main Results:
- Current 13 CODIS core loci are adequate for single-source profiles and international data sharing but insufficient for complex kinship analyses and mixture deconvolution.
- Expanded sets of 19 or more autosomal STR loci demonstrate superior performance in kinship searches and mixture analysis.
- Incorporating Y-chromosome STR (Y-STR) loci enhances paternal lineage tracing, mixture deconvolution, and kinship analysis, with DYS391 showing limited utility.
Conclusions:
- Further comprehensive studies are needed to inform decision-making regarding the construction of a new CODIS core loci set.
- The selection of CODIS core loci must prioritize supporting the needs of casework and forensic DNA database applications.
- Expanded STR loci sets, particularly those including Y-STRs, offer significant advantages for complex forensic investigations.
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