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Improving Analysis of "Trace DNA" Evidence

NCJ Number
Date Published
January 2023

This brief publication summarizes researchers' efforts to maximize DNA in low-yield situations and reduce costs through the use of direct polymerase chain reaction (PCR); it compares direct PCR to standard PCR; it suggests that results could result in simplified sample collection and submission guidelines for forensic laboratories; and provides a chart describing the steps of DNA processing.


Sometimes forensic labs can find ample DNA in the evidence collected at a crime scene. Other times, investigators are not as fortunate. Evidence samples with low amounts of DNA may not yield a profile that investigators can use to match or exclude potential suspects. Researchers, funded by the National Institute of Justice, are looking at direct polymerase chain reaction (PCR) as a potential solution. This DNA amplification method allows scientists to add a swab or sample directly to the PCR, which eliminates the loss of DNA that traditionally occurs during DNA extraction and quantification. Laboratories in the United States already use direct PCR for reference samples where the DNA donor is known, but current federal quality assurance standards keep them from using direct PCR for forensic evidence. The federal standards require all unknown forensic samples to undergo DNA quantification prior to amplification. The researchers found that the direct PCR method for trace DNA processing can produce complete DNA profiles in less than three hours and save labs approximately three to four hours of hands-on time and 25% in reagent costs. Although the process was not effective across all types of items, it was an improvement over standard DNA processing of trace DNA for seven of the 11 items tested. The results of this research inform the reevaluation of federal guidelines and could simplify sample collection and submission guidelines for forensic laboratories.

Date Published: January 1, 2023