Complex DNA mixtures from more than two individuals and/or profiles amplified with low-level quantities of DNA, can be challenging for the analyst to interpret. Dr. Coble first provided an overview of the technical issues with mixture interpretation including statistical analyses. Ms. Garcia then described the lessons learned in Texas as the state confronts one of the forensic DNA community’s elephants in the room—that DNA mixture interpretation is challenging and laboratories have not always interpreted complex mixtures properly. Ms. Garcia described how Texas became aware of the issue, what the Texas Forensic Science Commission did in response and how stakeholders have developed a plan to identify and notify potentially affected defendants in literally tens of thousands of cases. She then discussed what Texas observed regarding the crucial role of SWGDAM and the accrediting bodies, where the gaps in oversight are and what work remains to be done through the OSAC process. Ms. Garcia made the case for review of DNA mixture cases by any laboratory that may not have applied statistical methods properly (in particular the Combined Probability of Inclusion/Exclusion) and warned against viewing probabilistic genotyping software as a blackbox savior in light of what Texas has already observed for mixture recalculations using the software. Mr. Mills provided his thoughts on the issues in Texas from a laboratory director’s perspective.
- Lynn Robitaille Garcia
- Brady W. Mills
- Michael D. Coble
Funding for this Forensic Technology Center of Excellence webinar has been provided by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.
The opinions, findings, and conclusions or recommendations expressed in this webinar are those of the presenter(s) and do not necessarily reflect those of the U.S. Department of Justice.
Contact us at ForensicCOE@rti.org with any questions and subscribe to our newsletter for notifications.