DNA

A federal judge have unsealed the source code for a software program developed by NYC’s crime lab, exposing to public scrutiny a disputed technique for analysing complex DNA evidence.

The source code for a software program developed by New York City’s crime lab was made public last week, after scientists and defence attorneys raised concerns that flaws in its design may have resulted in innocent people going to prison. 

The Forensic Statistical Tool was first used back in 2011, where it was used frequently to link trace amounts of DNA to suspects or persons of interest for the succeeding five years. It’s not in use any longer, as it was superseded by new software in 2016. 

DNA evidence has long been a valuable tool in criminal investigations, and matching a defendant’s genetic material with a sample found on a weapon or at a crime scene has impressed many a judge and jury. But as new types of DNA analysis have emerged in recent years to interpret trace amounts or complex mixtures that used to be dismissed as hopelessly ambiguous, the techniques are coming under fire as overly ambitious and mistake-prone, writes Pro Publica. 

“Everybody who has been the subject of an FST report now gets to find out to what extent that was inaccurate,” said Christopher Flood, a defence lawyer who has sought access to the code for several years. “And I mean everybody — whether they pleaded guilty before trial, or whether it was presented to a jury, or whether their case was dismissed. Everybody has a right to know, and the public has a right to know.”

The code was first allowed out of the lab in 2016, but not for public disclosure. In a code review conducted at the request of the defence on another case, computer scientist Nathaniel Adams concluded: 

“I did not leave with the impression that FST was developed by an experienced software development team, especially in regards to adherence to coding conventions, use of general software development standards, or even basic good practices such as using consistent coding styles; attributing authorship to code segments; or writing automated software tests… the correctness of the behaviour of the FST software should be seriously questioned.”

Pro Publica argued that the code should be made public following Adam’s report, on the grounds that its integrity, and by extension the validity of perhaps hundreds of verdicts, was in serious question, reports Tech Crunch. 

This was agreed upon by judge Valerie Caproni, who lifted the protective order sealing the code from public view. 

If you’re interested, you can look into the complete source code for Forensic Statistical Tool here.