A lab technician may have mishandled critical DNA evidence in over 800 rape cases between 2001 and 2011, The New York Times reported Friday.
Supervisors at the medical examiner's office have found 26 cases to date in which the technician failed to detect the DNA evidence when some actually existed.
In seven of the cases, full DNA profiles were developed, and in one the new profile matched a convicted offender's sample, leading to an indictment a decade after the evidence was collected.
In two other instances, the new DNA evidence was linked to people already convicted or under suspicion.
"This is the first time we've had anything like this," said Ellen Borakove, a spokeswoman for the medical examiner's office which employs 48 technicians who conduct preliminary tests on rape kits that contain saliva, semen or blood collected from assailants.
The office handles about 1,500 sexual assault cases a year.
The review found that the technician sometimes overlooked stains, while at other times she identified stains but then made errors in the chemical test used to detect semen and reported not finding anything.
Dr.Mechthild Prinz, director of forensic biology at the medical examiner's office, told the Times that the technician's errors involved reporting false negatives, not false positives.
"We do know that nobody was wrongfully convicted," she said.
The office has not finished reviewing 412 cases out of 843 it intends to review.
The technician was not identified. She resigned in November 2011 after working there for nine years.