DNA decontamination protocols

Abstract

Aim: To determine the effectiveness of a cleaning protocol at removing DNA material from selected surfaces and items in a sexual assault examination room after deliberate contamination. A secondary aim is to determine the extent of background DNA by analysis of control samples. Background: The new Multi-Disciplinary Centre (MDC) in Dandenong, Victoria, includes two adjacent purpose-built examination suites dedicated for sexual assault examinations. The effectiveness of current cleaning protocols at removing DNA material from the sexual assault examination suites at the MDC remains untested. Method: Standardised and diluted single-donor blood samples, which when dried were not visible to the naked eye, were smeared onto pre-determined surfaces and items in a previously cleaned and sealed sexual assault examination room. Control samples were taken from the pre-determined sites before and after contamination using certified DNA free swabs dampened with DNA free water. A forensic clean was requested in the normal fashion and a trained cleaner, who was blinded to the deliberate contamination, cleaned the suite in accordance with established protocols after a sexual assault examination at the MDC. Within 12–24 hours of cleaning, samples were obtained from the previously contaminated sites. All samples, including positive and negative controls, were forwarded to the laboratory for nuclear DNA analysis. The current cleaning protocols and the results will be presented. Discussion: Potential contamination from the facility in which forensic samples are obtained can have significant impact on their forensic integrity and their admissibility in and reliance by the courts. A cleaning regimen that reliably removes sources of biological material from an examination room between examinations reduces, but does not eliminate, the chance of cross-contamination.