Decontamination of Crime Scene Equipment: Evaluating Current Methods and Determining Best Practices, United States, 2019-2020

A 2016 needs assessment conducted by the National Institute of Standards and Technology's Organization of Scientific Area Committees for Forensic Science (NIST/OSAC) Crime Scene Investigation (CSI) Subcommittee identified the decontamination of crime scene equipment as a gap that must be addressed. Currently, there are no widely accepted standard operating procedures (SOP) and/or best practices for crime scene investigators to follow regarding equipment decontamination. Furthermore, to date, there has been no peer-reviewed published research to assess the effectiveness of the different decontamination methods that are currently employed by crime laboratories and law enforcement agencies involved in crime scene investigations. Ineffective decontamination of crime scene equipment has the potential to lead to cross-contamination between scenes as well as secondary transfer to evidence after contact with equipment. With increased sensitivity of current DNA analysis protocols, the ineffective decontamination of CSI equipment has implication for wrongful convictions due to potential secondary DNA transfer.

To address this gap, and in response to the NIST/OSAC needs assessment, RTI International (RTI) performed a comprehensive evaluation of several decontamination methods on commonly used CSI equipment to provide the community with evidence-based recommendations of effective decontamination protocols. RTI identified reusable CSI equipment that is most likely to be contaminated with biological material after use at a crime scene based on literature searches, crime laboratory SOP reviews, and discussions with crime scene practitioners. Seven types of crime scene-related equipment were used to determine the extent of the effectiveness of nine frequently used decontamination methods. The total amount of DNA remaining on the equipment after a controlled decontamination was quantified using Quantifiler Trio DNA Quantification Kit and processed for short tandem repeat markers (STRs) with GlobalFiler. Quantifiler Trio includes a degradation index (DI) that provides an estimation of the quality of DNA in potentially degraded samples.