31-May-2025

What is the Accuracy of a DNA Match?

In everyday life we are faced with uncertain binary outcomes based on numerical scores. In diagnosing ovarian cancer, for example, a high CA-125 blood test score indicates cancer, while a low score suggests otherwise. More accurate diagnostic tests produce scores that can better distinguish between the two outcomes.

The same is true for forensic DNA match. A likelihood ratio (LR) match statistic puts a numerical score to a DNA comparison. A large score points to a match, while a small score doesn't. More accurate probabilistic genotyping can better classify DNA match based on the LR score.

DNA match classification accuracy can be determined directly from a genotype. Highly accurate genotypes have widely separated match and nonmatch curves. Less accurate genotypes don't distinguish match and nonmatch as well. TrueAllele's validated classification ability is shown below.

Some experts opposing reliable DNA evidence use non-scientific arguments. They often ignore crucial match statistic information, like magnitude and error rate. In February 2025, Cybergenetics TrueAllele analyst Jennifer Bracamontes gave a scientific AAFS talk on "Overcoming unscientific opposing arguments using relevant data". She showed how quantifying DNA match classification accuracy can overcome specious arguments.

In April 2025, TrueAllele chief scientist Dr. Mark Perlin spoke to a George Mason University forensic science class using the same PowerPoint slides. In his lecture video, Dr. Perlin first introduces DNA match classification and its accuracy. Then, like Jennifer, he applies these concepts to federal cases (Johnson, Sandoval, Mills) where Cybergenetics overcame TrueAllele court challenges by using better science.