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Comparing Standard and Selective Degradation DNA Extraction Methods: Results From a Field Experiment With Sexual Assault Kits

NCJ Number
Date Published
January 2017
10 pages
This study evaluated selective degradation methods for DNA extraction, using actual case work from a sample of previously unsubmitted sexual assault kits (SAKs) in Detroit, Michigan.
A growing number of U.S. cities have large numbers of untested SAKs in police property facilities. Testing older kits and maintaining current case work will be challenging for forensic laboratories, creating a need for more efficient testing methods. The current study randomly assigned 350 kits to either standard or selective degradation testing methods and then compared DNA testing rates and CODIS entry rates between the two groups. Continuation-ratio modeling showed no significant differences, indicating that the selective degradation method had no decrement in performance relative to customary methods. Follow-up equivalence tests indicated that CODIS entry rates for the two methods could differ by more than ±5 percent. Selective degradation methods required less personnel time for testing and scientific review than standard testing. (Publisher abstract modified)

Date Published: January 1, 2017