Doubt cast on renowned lab’s DNA analysis

Officials in New York asked to investigate two techniques used in thousands of cases

NEW YORK— Two techniques for analyzing DNA evidence that were once considered cutting edge are now under fire amid questions about their reliability, and criminal defence attorneys in New York have asked a state agency to investigate the renowned lab that once used both methods.

The New York City medical examiner’s lab developed one of the techniques and became a leader in sophisticated DNA examinations partly because of its work identifying the remains of Sept. 11 victims.

Both techniques have been phased out in favour of new technology. But the lab says it has used its forensic statistical tool (FST) developed inhouse in 1,350 cases over the past six years and used what’s called low copy number analysis in about 3,450 cases over the past 11 years. Once, New York was the only lab in the country that used the latter method.

Attorneys for the Legal Aid Society and Federal Defenders of New York asked the New York state inspector general’s office to investigate in a Sept. 1 letter.

Legal Aid Society attorney Julie Fry said low copy number analysis is “like making a copy of a copy of a copy. Eventually it’s going to be faded.”

The lawyers also say they believe the lab manipulated data while test- ing the low copy number technique and made false statements on methodology to the Commission on Forensic Sciences, which oversees labs in the state.

The letter was first reported by the New York Times and ProPublica.

Chief medical examiner Dr. Barbara Sampson wrote in a post published Wednesday on the website Medium that the two methods were discarded to meet changing FBI requirements and to reflect new, better science and were not phased out because of inaccurate results.

Many prosecutors and forensic experts hail the two techniques as powerful tools that can help close cases. But critics, including the FBI, argue they are inconclusive and unreliable.

There is no clear case law on the merits of the science.