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Assessment of the Role of DNA Repair in Damaged Forensic Samples

NCJ Number
Date Published
November 2014
9 pages
This study developed protocols to damage DNA in its native state, generated a pool of candidate samples for repair that more likely emulate authentic forensic samples, and assessed the ability of the PreCRTM Repair Mix to repair the resultant lesions.
Previous studies on DNA damage and repair have involved in vitro laboratory procedures that induce a single type of lesion in naked templates. Although repair of singular, sequestered types of DNA damage has shown some success, forensic and ancient specimens likely contain a number of different types of lesions. Complexed, native DNA is more difficult to damage than naked DNA. Modified procedures included the use of higher concentrations and longer exposure times. Three types of samples, those that demonstrated damage based on short tandem repeat (STR) profile signals, were selected for repair experiments: environmentally damaged bloodstains, bleach-damaged whole blood, and human skeletal remains. Results showed trends of improved performance of STR profiling of bleach-damaged DNA; however, the repair assay did not improve DNA profiles from environmentally damaged bloodstains or bone, and in some cases resulted in lower RFU values for STR alleles. The extensive spectrum of DNA damage and myriad combinations of lesions that can be present in forensic samples appears to pose a challenge for the in vitro PreCRTM assay. The data suggest that the use of PreCR in casework should be considered with caution due to the assay’s varied results. (Publisher abstract modified)
Date Published: November 1, 2014