Tech

Accused murderer wins right to check source code of DNA testing kit used by police

A New Jersey appeals court has ruled that a defendant in a murder case is entitled to review proprietary genetic testing software to challenge evidence presented against him.

Attorneys defending Corey Pickett, charged following a fatal Jersey City shooting that occurred in 2017, have been trying to examine the source code of a software program called TrueAllele to assess its reliability. The software helped analyze a genetic sample from a weapon that was used to tie the defendant to the crime.

The maker of the software, Cybergenetics, has insisted in lower court proceedings that the program’s source code is a trade secret. The co-founder of the company, Mark Perlin, is said to have argued against source code analysis by claiming that the program, consisting of 170,000 lines of MATLAB code, is so dense it would take eight and a half years to review at a rate of ten lines an hour.

The company offered the defense access under tightly controlled conditions outlined in a non-disclosure agreement, which included accepting a $1m liability fine in the event code details leaked. But the defense team objected to the conditions, which they argued would hinder their evaluation and would deter any expert witness from participating.

With the two sides unable to reach an agreement, the lower court judge hearing the case denied the defense’s motion to vet the source code, without sufficiently addressing the defense arguments. That prompted the defense to appeal.

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Those arguing on behalf of the defense cited past problems with other genetic testing software such as STRmix and FST (Forensic Statistical Tool). Defense expert witnesses Mats Heimdahl and Jeanna Matthews, for example, said that STRmix had 13 coding errors that affected 60 criminal cases, errors not revealed until a source code review.

They also pointed out, as the appeals court ruling describes, how an FST source code review “uncovered that a ‘secret function . . . was present in the software, tending to overestimate the likelihood of guilt.'”

On Wednesday, the appellate court sided with the defense [PDF] and sent the case back to a lower court directing the judge to compel Cybergenetics to make the TrueAllele code available to the defense team.

“Without scrutinizing its software’s source code – a human-made set of instructions that may contain bugs, glitches, and defects – in the context of an adversarial system, no finding that it properly implements the underlying science could realistically be made,” the ruling says.

Kit Walsh, senior staff attorney for the Electronic Frontier Foundation, hailed the appellate ruling. “No one should be imprisoned or executed based on secret evidence that cannot be fairly evaluated for its reliability, and the ruling in this case will help prevent that injustice,” she said in a blog post.

If TrueAllele is found wanting, presumably that will not affect the dozen individuals said to have been exonerated by the software. ®


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