Analyzing the viability of direct PCR for use in conjunction with cyanoacrylate enhanced fingerprints

Abstract

Efficient methods for DNA analysis are desperately needed in laboratories due to the influx in DNA analysis requests. The current DNA processing methods are costly, time consuming, and involve multiple tube changes, increasing the risk of contamination. However, the use of direct PCR can simplify the DNA analysis process by eliminating the extraction, purification and quantitation steps. Presently, the FBI Quality Assurance Standard 9.4 requires all evidence samples to be quantitated. As a result, the direct PCR method of DNA processing cannot be implemented on evidence samples at this time. Direct PCR presents the opportunity to provide efficient DNA analysis, making the investigation of this process an important endeavor for the forensic community. This study sought to evaluate the ability of direct PCR to generate DNA profiles from fingerprints that have been previously enhanced using cyanoacrylate. Traditional methods of DNA analysis used on fingerprints post chemical processing have resulted in full DNA profiles. In addition, direct PCR has been successful on a wide variety of samples containing potential inhibitors, even those visualized with various dactyloscopic powders. No studies have assessed the ability of using direct PCR to acquire DNA profiles from cyanoacrylate treated fingerprints, representing a gap in knowledge for the forensic community. An area of concern for the use of direct PCR is the loss of purification steps meant to remove PCR inhibitors, which could be problematic for analysis of chemically processed fingerprints. Therefore, the assessment of the viability of direct PCR on these types of evidence samples is of critical importance. Participants deposited fingerprints onto glass slides that were subsequently treated with cyanoacrylate. 60 samples were processed using direct PCR and 60 samples were processed through a traditional extraction method. Results were evaluated based on percent recoverability, calculated based on the number of alleles observed over the number of alleles expected. Traditional methods were shown to have the greatest success overall with 53% of samples having at least one correct allele call, however direct PCR showed some success with only 23%. These results indicate that processing cyanoacrylate fumed fingerprint samples using direct PCR is possible and further experimentation and optimization could potentially increase these success rates.