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Cybergenetics DNA transfer testimony helps convict Pittsburgh shooter

Pittsburgh, PA

On August 24, 2015, Daren Scott, 25, of Munhall was shot in Homestead near the Carnegie Library. He ran, collapsed and died. The shooter’s dismantled handgun was found in an apartment where defendant Carlos Harris stayed. The murder weapon parts were wrapped in a t-shirt and a towel.

DNA was found on the gun parts and cloth wrappers. The county lab produced DNA mixture data. But the lab could not tie the gun, containing DNA from four or five people, to the defendant. In court, their analysts said the lab lacked statistical tools needed to connect complex mixtures to Harris.

Cybergenetics analyzed the lab’s DNA mixture data from the gun parts and wrappers. Their TrueAllele® computer analysis of the t-shirt and towel was conducted and reported in one day. The computer connected Mr. Harris to both gun parts and both wrappers, with match statistics ranging from millions to quadrillions.

On May 15, Cybergenetics Dr. Mark Perlin testified about the TrueAllele results in a non-jury trial. Deputy District Attorney Christopher Avetta introduced the DNA mixture evidence linking Harris to the gun. The defense attorney argued that “DNA transfer” had innocently transferred Harris’ DNA from the cotton wrappings onto the handgun parts. But the science did not agree.

Dr. Perlin cited the forensic science literature. Research has shown that DNA moves easily from a hard non-porous surface (e.g., gun steel) to a soft porous surface (e.g., cotton fabric). But not the other way around – just one molecule in five thousand will go from cotton to steel. DNA transfer can occur, but was extremely unlikely in this case.

On May 21, Allegheny County Common Pleas Judge Thomas Flaherty found Carlos Harris guilty of third-degree murder. Harris will be sentenced on August 7.

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