Setting the Record Straight on DNA Science

By NYC Chief Medical Examiner Dr. Barbara Sampson

The New York City Office of Chief Medical Examiner operates the largest and most advanced public DNA crime laboratory in North America. We are proud to set the highest standards for independent science and to share our expertise with other jurisdictions in the neutral service of justice, without favor to prosecution or defense.

The independent science performed by OCME produces findings that may serve both the prosecution and the defense in the criminal justice system. In fact, defense attorneys including the Legal Aid Society have asked OCME to run low copy number (LCN) testing and the Forensic Statistical Tool (FST) for their cases, and the FBI has also requested the use of these techniques for their casework. No serious discussion of these techniques can fail to mention the numerous high-profile examples of exonerations of innocent defendants made possible thanks to LCN and FST.

In early 2017, our laboratory upgraded its technology in order to comply with a new requirement that expanded the number of core loci DNA profiles must have (from 13 to 20) in order to be eligible for upload to the Combined DNA Index System, the national DNA database system maintained by the Federal Bureau of Investigation. These upgrades included a transition to the new chemical kit of Promega PowerPlex Fusion and to a new probabilistic gene typing software, STRMix. The increased sensitivity in DNA testing made possible by these upgrades rendered two of our previous technologies, LCN testing and the FST, unnecessary, and therefore our lab phased out both techniques.

OCME announced these and other upgrades to participants in the criminal justice system who use the results of our analysis in late 2016, months before the changes took effect. Contrary to the allegations in an article today in The New York Times, the upgrades were not prompted by inaccuracies in the FST and LCN techniques, but rather by the imperative to meet the changing FBI requirements. As scientists who work with facts and evidence know, the mere instance of a change is not an acknowledgement of a problem.

OCME stands by the proven reliability of LCN and FST and their general acceptance in the scientific community. Each technique has been intensively reviewed and approved for use in casework by the state-established oversight agency, including a panel of distinguished scientific experts, the DNA subcommittee of the New York State Commission on Forensic Science. The techniques also have been upheld by multiple courts.

DNA science has the power to convict the guilty and exonerate the innocent, but in many legal proceedings, DNA is one factor among many considered by attorneys, judges, and juries. The role of OCME is to perform the DNA science with accuracy and independence.

Our DNA laboratory is a world-class facility. The lab has been accredited by the American Society of Crime Laboratory Directors/Laboratory Accreditation Board (ASCLD/LAB) since 1995, and in the most recent renewal of its international accreditation with ASCLD/LAB in late 2015, the lab received a perfect score, a rare achievement for laboratories of our size and complexity. As part of the rigorous accreditation process, a team of outside experts reported zero findings during its on-site assessment of the lab’s adherence to more than 1,000 directives and specifications.

With our dedication to continuous improvement and commitment to independence, OCME will continue to be a leader providing science in the service of justice.