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The probative power of DNA mixtures

M.W. Perlin, "The probative power of DNA mixtures", Louisiana District Attorneys Association 39th Annual Conference, Destin, FL, 27-Jun-2016.


Talk

PowerPoint presentation with live audio recording of Dr. Perlin's talk.



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Abstract

Mixtures are evidence items containing DNA from two or more people. Crime laboratories generate excellent data from DNA mixtures. However, they often cannot interpret their data to calculate DNA match statistics for court. Developed in 1999, and widely used in Louisiana, TrueAllele computer technology solves the DNA mixture interpretation problem.

TrueAllele separates crime lab data into the genetic types (or "genotypes") of each person who contributed their DNA to the mixture. The separation is objective – the computer does not know the suspect’s genotype when it solves the problem. Uncertainty is represented using probability. After separation, TrueAllele compares evidence and reference genotypes to determine accurate DNA match statistics.

TrueAllele has been admitted into evidence after Daubert challenge by a Baton Rouge trial court, and in eight other states. Louisiana has seen TrueAllele reports in over twenty five criminal cases. The computer’s reliability has been established in over thirty validation studies. Two Louisiana crime labs have purchased TrueAllele, and are currently bringing the system on-line for interpreting their own DNA mixture evidence.

When properly interpreted, mixtures can be highly probative, establishing the presence of multiple people at a crime scene. The talk will describe TrueAllele and how it works, illustrating its use in Louisiana criminal convictions, including:

  • State v. Chattley Chesterfield (Baton Rouge), second degree murder
  • State v. Christopher Hutsell (New Orleans), second degree murder
  • State v. Henry Lewis, Jr. (Gonzales), juvenile molestation
  • State v. Corderrius Mitchell (Baton Rouge), second degree murder
  • State v. Reokenski Thomas & Hilton Wilson (Ville Platte), first degree murder

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