The New Times reports that the New York City Medical Examiner’s office is reviewing over 800 rape cases where DNA evidence was possibly mishandled by a lab technician.  Yes, over 800 rape cases over a period of 10 years from 2001-2011.

The articles details the technician’s responsibilities.  The technician had two responsibilities when processing rape kits: She had to snip cuttings from swabs taken from victims’ bodies and place them in test tubes for DNA analysis by more experienced lab workers.  She also inspected the victims’ clothing, usually underwear, for stains that might indicate DNA. Sometimes she overlooked stains, the review found. At other times, she identified stains, but then botched the chemical test used to detect semen and reported finding nothing.  Over a span of two years, lab officials thought they had discovered all the errors but kept finding more.

The lab’s stance at this point seems to be no harm, no foul.  Dr. Mechthild Prinz, the director of forensic biology at the medical examiner’s office, said the errors involve false negatives, not false positives.   “We do know that nobody was wrongfully convicted,” she added.  The office also cited two cases where re-testing led to the discovery of a DNA profile identifying the perpetrator.

But while confident that no one has been wrongfully convicted, the lab also admits that DNA evidence was commingled in 19 rape investigations.  The Times got this explanation – “Our guess is the technician had both kits open at the same time, and when she was reassembling the case files, evidently she had misplaced the evidence items from one kit to another,” Eugene Lien, a quality assurance manager with the medical examiner’s office, told a state oversight board last year. It was not “standard policy at all,” he added, for a technician to have two cases open at once.  Asked in an interview about the risk of cross-contamination, Dr. Prinz said: “It’s extremely unlikely. I don’t think that is a risk.”  My concern is Dr. Prinz’ steadfast confidence that the errors or the commingling did not lead to any wrongful convictions.

Willam Thompson, a criminology professor at UC-Irvine view and someone is familiar with wrongful convictions cases, isn’t as convinced as Dr. Prinz.  He told the Times that  “accidental transfer in a lab of DNA from one sample to another sample is not a rare event.” He estimated that, nationwide, cross-contamination of samples is found at a rate 1 in 100 cases or higher.  What Prof. Thompson knows and what Dr. Prinz fails to understand is that wrongful convictions can occur from this type of cross-contamination.

My concern is that Dr. Prinz seems really confident that no one has been wrongfully convicted.  But do they really know?  And  as others noted, is this indicative of other issues in the lab?   The lab tries to reassure us that the problem is isolated and not to worry.   But the lab, during their investigation, admitted that the technician’s errors kept appearing the further they kept digging.

As with all cases where there are serious errors at labs, the main question is whether this is an isolated case or the tip of the iceberg.   The lab’s spokesperson told the Times that “We have an enormous public trust to produce accurate results, and we have accordingly dedicated ourselves to do the most comprehensive review of her cases.”   But the emphasis is on “her” (the lab technician in question) cases.   Will the lab take the right steps and do a thorough review (either internally or using an outside organization) of all cases?   Only then can public trust be entirely restored and assured that no wrongful convictions took place.

Interestingly, a crime lab worker in Iowa was fired for mishandling fingerprint data.   The lab caught the errors through internal reviews but also emphasized that no wrongful convictions resulted.