An assessment of DNA contamination risks in New York City Medical Examiner facilities

DNA evidence holds an important position in criminal investigations and proceedings. The polymerase chain reaction (PCR) is often utilized to amplify polymorphic regions of DNA which are subsequently typed to produce distinct genotypes. The sensitivity of PCR-based techniques provides a major advantage over other DNA or conventional serological typing systems. Samples containing quantities of DNA in the picogram range are often typed. However, the unprecedented sensitivity of PCR is often cited as a criticism. One concern is that the interpretation of PCR typing can be affected by DNA contaminants from foreign sources. In this report, the level of DNA contamination in New York City Medical Examiner facilities and its potential affects on HLA-DQA1 typing were assessed. Two related studies conducted over a five week period measured and typed HLA-DQA1 from accumulated DNA on autopsy room and Forensic DNA Laboratory structures. The potential for DNA contamination from airborne sources was also evaluated in the autopsy suites. This study demonstrated the presence of small amounts of DNA on structural surfaces, but little evidence of airborne DNA contamination.