Federal Court Says 'Touch DNA' Analysis Is Mostly Guesswork That Can't Be Used As Evidence

DNA was supposed to be the gold standard of criminal evidence. And it can be, but only under very specific circumstances rarely found in the messy world of crime scenes. DNA evidence is easily contaminated by the people handling the evidence, not to mention anyone else who's been at the crime scene. This has resulted in law enforcement agencies spending years chasing phantom criminals, only to find out the DNA investigators kept finding at crime scenes came from other officers, first responders, or even the person packing their DNA kits back at the manufacturer.

But the myth that DNA evidence is nigh-infallible persists. Some of this is due to the inscrutable nature of the processes that turn stray cells into evidence. Some of this is due to forensic experts overstating the certainty of their findings.

When DNA evidence is pretty much the only evidence holding a case together, the evidence had better be solid. A federal court in Michigan has found that the framework behind one company's (STRmix) DNA evidence testing is a cobbled-together mess that sounds nice and science-y, but isn't much more than overly-educated guesswork. (via Grits For Breakfast)

The ruling [PDF] on the defendant's Daubert motion (a motion that seeks to exclude qualified evidence or testimony) opens with a recounting of the alleged criminal act and the less-than-stellar handling of pretty much the only evidence the prosecution is using to make its case.

Defendant Daniel Gissantaner is charged with a single offense of felon in possession of a firearm, subject to a penalty of not less than 15 years’ and up to life imprisonment; not more than a $250,000 fine; and supervised release of not more than 5 years. The case against Gissantaner rests fundamentally, if not entirely, on a small amount of “touch” DNA taken from a gun in a locked cedar chest during a search of Gissantaner’s house on September 25, 2015, following a dispute with his neighbors over parking in a shared driveway, and police officers’ response to the neighbor’s 911 call. The locked chest containing the gun belonged to Gissantaner’s wife’s daughter’s boyfriend, Cory Patton. Patton, also a convicted felon, had the only key to the locked chest, which was located in Patton’s upstairs bedroom and opened by him at police officers’ request during the search. According to the various police reports, Patton gave conflicting statements about the gun, stating that he heard an argument, went outside, and took the gun away from Gissantaner, but also stating that he never saw Gissantaner with the gun, he found it on the kitchen counter after the argument, and then placed it in the chest.

It seems like the most simple explanation would be that it was Patton's gun found in Patton's locked chest that only Patton had a key to. The "conflicting statements" might just have been lies told by Patton because he didn't want to go away for 15 years minimum. The decision doesn't say whether Patton's DNA was ever tested to see if his was present on the gun. All it says is the police handled the evidence sloppily and turned it over to the forensic lab.

The evidentiary handling of the gun is far from pristine. It appears that the gun was moved or handled by at least one police officer before it was taken into evidence. There are also some unexplained delays and unknown whereabouts of the gun between the time it was taken from Gissantaner’s house and the submission to the Michigan State Police (MSP) lab for analysis.

From there, the "touch-DNA" analyst arrived at the conclusion that it was "49 million more times likely" that Gissanter's DNA was present on the gun, rather than yet another unrelated person's. The only other contributors to the DNA found on the gun were "two unrelated, unknown contributors." Even if accurate, this only shows Gissanter had touched the gun. It doesn't necessarily mean it was Gissanter's gun.

There are still scientifically-sound methods for DNA testing, like the use of rape kits which already controls for one known DNA sample