Forensic DNA Research and Development: Tools for the Crime Lab I: Compromised DNA Evidence Development, Characterization and Performance of New MiniSTR Loci for Typing Degraded Samples (on behalf of NIST)

Forensic DNA analysts often perform short tandem repeat (STR) typing on highly degraded biological material and then turn to mitochondrial DNA testing if many or all of the STRs fail. The commercially available kits for multiplex amplification of the 13 CODIS STR loci usually exhibit allele or locus-dropout for larger sized loci with degraded DNA or samples containing PCR inhibitors. Recently, a number of studies have demonstrated an increased success for the analysis of degraded DNA specimens from mass disasters (or degraded forensic evidence) when smaller sized PCR amplicons are utilized. One advantage of generating smaller sized PCR products (miniSTRs) for the CODIS loci is that it is possible to obtain fully concordant results to the commercial kits while improving successful analysis of degraded DNA. However, many of the CODIS core loci have large allele ranges (e.g., D21S11 and FGA) or have “unclean” flanking regions for successful primer hybridization that make it impossible to create miniSTRs. The Human Identity Project Team in the DNA Measurements Group at NIST has examined a battery of new potential STR loci (called non-CODIS, NC) that can be made less than 150 bp in size (in most cases) and would therefore be helpful in testing highly degraded or low copy number DNA samples. Project scientists have also characterized these markers across more than 600 population samples. In this presentation, presenters will discuss the development, characterization, and performance of these new miniSTRs and their impact on the global forensic DNA community.