Crime

DNA -- Debate Or Debacle, And Why A Good Judge Makes All The Difference

When infallible science turns out to be not so infallible, the consequences can be grave.

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I didn’t know much about DNA until I had to try a murder case and part of the evidence was based on a minute amount of DNA found on the grip of a gun.

Not only was the DNA amount tiny, but it turned out to be a mixture from two or more human sources. I had to not only familiarize myself with DNA vocabulary (alleles, loci, low-copy number, testing methods, picograms, transference, etc.), but I also had to understand and challenge how the New York City Office of Chief Medical Examiner (OCME) used two controversial methods — “high-sensitivity testing” and the Forensic Statistical Tool (FST) — to reach its conclusions.

Every lab has different standards regarding the minimum amount of DNA needed to make a test valid. When the amount of DNA recovered is small, it’s measured in picograms — one picogram equals one trillionth of a gram. While many labs won’t test below 100 picograms, OCME tested as low as 20. With such self-asserted leeway, they were getting calls from labs all over the country to test their low-quantity DNA. The issue arose — was their methodology correct?

Copying small amounts of DNA in order to read it better is not, in and of itself, controversial. However, the OCME decided to copy the small quantities more times than standard labs — 31 times instead of 28. The problem is that amplifying small quantities can often distort what’s actually there. Think of blowing up a photo. At some point the exaggerated size of each pixel distorts the image rather than clarifies it.

The OCME then developed another controversial testing aid, the Forensic Statistical Tool (FST), a software program designed to calculate the likelihood that a defendant’s DNA was present in an amplified mixture. The FST produced a ratio of how likely it was that a defendant’s skin cells were among those found on, in my case, a gun. The numbers generated were often astronomical. For example, even if only 22 picograms of DNA were recovered (again a number below what most labs would even consider testable), and even if that DNA was a mixture of at least three people, the FST result might show, to quote from the transcript in my case:

It is 43,100 times more probable that the sample originated from Vincent P. [my client] and two unknown unrelated persons than if it originated from three unknown, unrelated persons. Therefore, there is very strong support that Vincent P. and two unknown unrelated persons contributed to the mixture, rather than three unknown unrelated persons.

Wow, what a mouthful. It’s hard enough explaining the burden of proof to a jury, let alone the intricacies of language like “unknown, unrelated persons” and a number as high as “43,100 more probable.” (As a bit of background, 43,100 isn’t actually a high number in this context. Likelihood probability numbers can reach into the trillions.)

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The OCME methodology was being challenged by defense attorneys in Frye hearings (hearings that test the validity of novel scientific methods) in other courts at the time I went to trial, but my judge decided not to wait. Instead of doing his own hearing in our case, or at least waiting for the ruling from another lengthy hearing being done by a judge in the same building, my judge forced our trial to start and let in the DNA evidence. His decision was based on the cursory single-page decisions of other judges of concurrent jurisdiction who had piggy-backed their decisions on similarly curt rulings by yet other judges, none of whom had held full-scale Frye hearings.

Due in large part to the introduction of the questionable DNA evidence, my client was convicted.

About six months later, the judge involved in the lengthy Frye hearing (in the same building as my case) decided that the OCME methods regarding DNA testing were NOT scientifically sound and excluded the DNA in that case. Judge Mark Dwyer had heard testimony over the course of two years from dozens of experts, read the reports, analysis, testing-validation studies, and took his time to ponder, consider and rule. That’s what was required, and that’s what he did.

Now OCME is coming to grips with its own faulty practices. Without admitting such, they’ve changed the program they use for their statistical analysis and are reducing the number of cycles in their amplification process. With criticism coming from former employees and perhaps pushed by Judge Dwyer’s adverse ruling, OCME has, on its own, revised its practices. The two scientists who designed FST and the high-sensitivity testing on low quantity DNA have resigned, and OCME has instituted methods more in keeping with the tried and true standards of the FBI. (See the excellent New York Times/ProPublica story on this from last week.)

OCME methods were questionable from the get-go, yet only one judge took the defense challenge seriously. While most judges like to sustain the status quo, Judge Dwyer spent the time necessary to consider testimony over the course of two years then think long and hard about it. Bravo to Judge Dwyer, but wouldn’t it be great if more judges showed the same intellectual curiosity and guts to challenge the “standard practices” when persuasive evidence is presented?

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OCME is a powerful organization. Experts I spoke to who’d left OCME, precisely because of the lab’s questionable practices, were literally afraid to testify in my case because of possible repercussions. I’m not talking about physical harm like being beat up; I’m talking about career repercussions to them and their family members. One woman, Dr. Marina Stajic, who supported a proposal in favor of turning over validation studies to defense attorneys, was later fired. (She’s now suing.)

Eventually, I hired an expert from Scotland to testify in my case. (Dr. Allan Jamieson did a fabulous job, but with his strong Scottish accent, it jarred jurors each time he referred to D-N-EEE.)

During my trial, the OCME expert testified about the infallibility of their method, claiming it was more advanced than even how the FBI conducted its testing. Without being willing to disclose the basis for why their practice was sound (and most judges did not compel them to do so in spite of requests from defense attorneys due to what the OCME said were “copyright” issues), the OCME clung to this position. Their experts testified around the state and put forth conclusions that may have been downright wrong.

A lot of people have been convicted based on this faulty DNA science. It’s time now to revisit these cases.

Vincent P., my client from a hard-working African immigrant family, was 16 years old when he was allegedly involved in a gang shooting that left a 14-year-old boy dead on a playground in Brooklyn. The evidence was not black and white. There was plenty of reasonable doubt. The jury was out for more than a week. According to one juror I spoke to after, the DNA evidence pushed them to convict.

Many jurors cried when they convicted Vincent, and one juror writes him in prison. It was a tragedy all around — the death of one young boy, and the waste of another’s young life for a crime he may not have committed. (Vincent has always denied being involved in the shooting.) The judge mercilessly sentenced him to 40 years to life.

Maybe this new skepticism about OCME’s past testing methods will open another door on appeal not only for Vincent, but also for the many others who’ve been convicted on so-called infallible science that turned out to be not so infallible.

Traces of Crime: How New York’s DNA Techniques Became Tainted [New York Times / ProPublica]

Toni Messina has tried over 100 cases and has been practicing criminal law and immigration since 1990. You can follow her on Twitter: @tonitamess.

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