Evidence mounting that DNA matching is more of an art than a science due partly to proprietary algorhythms

Dror and Hampikian gave the DNA evidence to 17 lab technicians for examination, withholding context about the case to ensure unbiased results. All of the techs were experienced, with an average of nine years in the field. Dror and Hampikian asked them to determine whether the mixture included DNA from the defendant. In 2011, the results of the experiment were made public: Only one of the 17 lab technicians concurred that the defendant could not be excluded as a contributor. Twelve told Dror and Hampikian that the DNA was exclusionary, and four said that it was inconclusive. In other words, had any one of those 16 scientists been responsible for the original DNA analysis, the rape trial could have played out in a radically different way. Toward the end of the study, Dror and Hampikian quote the early DNA-testing pioneer Peter Gill, who once noted, “If you show 10 colleagues a mixture, you will probably end up with 10 different answers” as to the identity of the contributor. (The study findings are now at the center of the defendant’s motion for a new trial.)


The case against Anderson started when police matched biological matter found under Kumra’s fingernails to Anderson’s DNA in a database. Anderson was held in jail for five months before his lawyer was able to produce records showing that Anderson had been in detox at a local hospital at the time of the killing; it turned out that the same paramedics who responded to the distress call from Kumra’s mansion had treated Anderson earlier that night, and inadvertently transferred his DNA to the crime scene via an oxygen-monitoring device placed on Kumra’s hand


DNA transfer—the migration of cells from person to person, and between people and objects—is inevitable when we touch, speak, do the laundry. A 1996 study showed that sperm cells from a single stain on one item of clothing made their way onto every other item of clothing in the washer. And because we all shed different amounts of cells, the strongest DNA profile on an object doesn’t always correspond to the person who most recently touched it. I could pick up a knife at 10 in the morning, but an analyst testing the handle that day might find a stronger and more complete DNA profile from my wife, who was using it four nights earlier. Or the analyst might find a profile of someone who never touched the knife at all. One recent study asked participants to shake hands with a partner for two minutes and then hold a knife; when the DNA on the knives was analyzed, the partner was identified as a contributor in 85 percent of cases, and in 20 percent as the main or sole contributor.


In 2011, Legal Aid requested a hearing to question whether the software met the Frye standard of acceptance by the larger scientific community. To Goldthwaite and her team, it seemed at least plausible that a relatively untested tool, especially in analyzing very small and degraded samples (the FST, like TrueAllele, is sometimes used to analyze low-copy-number evidence), could be turning up allele matches where there were none, or missing others that might have led technicians to an entirely different conclusion. And because the source code was kept secret, jurors couldn’t know the actual likelihood of a false match.

At the hearing, bolstered by a range of expert testimony, Goldthwaite and her colleagues argued that the FST, far from being established science, was an unknown quantity. (The medical examiner’s office refused to provide Legal Aid with the details of its code; in the end, the team was compelled to reverse-engineer the algorithm to show its flaws.)


In 2012, shortly after Legal Aid filed its challenge to the FST, two developers in the Netherlands, Hinda Haned and Jeroen de Jong, released LRmix Studio, free and open-source DNA-profiling software—the code is publicly available for other users to explore and improve.

Erin Murphy, of NYU, has argued that if probabilistic DNA typing is to be widely accepted by the legal community—and she believes that one day it should be—it will need to move in this direction: toward transparency.

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