Assessing the impact of common forensic presumptive tests on the ability to obtain results using a novel rapid DNA platform.

The rise of DNA evidence to the forefront of forensic science has led to high sample numbers being submitted for profiling by investigators to casework laboratories: bottleneck effects are often seen resulting in slow turnaround times and sample backlog. The ParaDNA(®) Screening and Intelligence Tests have been designed to guide investigators on the viability of potential sources of DNA allowing them to determine which samples should be sent for full DNA analysis. Both tests are designed to augment the arsenal of available forensic tests for end users and be used concurrently to those commonly available. Therefore, assessing the impact that common forensic tests have on such novel technology is important to measure. The systems were tested against various potential inhibitors to which samples may be exposed as part of the investigative process. Presumptive test agents for biological materials (blood, semen and saliva) and those used as fingerprint enhancement agents were both used. The Screening Test showed a drop in performance following application of aluminium powder and cyanoacrylate (CNA) on fingerprints samples; however this drop in performance was not replicated with high template DNA. No significant effect was observed for any agent using the Intelligence Test. Therefore, both tests stand up well to the chemical agents applied and can be used by investigators with confidence that system performance will be maintained.

Applicability of the ParaDNA(®) Screening System to Seminal Samples.

Seminal fluid represents a common biological material recovered from sexual assault crime scenes. Such samples can be prescreened using different techniques to determine cell type and relative amount before submitting for full STR profiling. The ParaDNA(®) Screening System is a novel forensic test which identifies the presence of DNA through amplification and detection of two common STR loci (D16S539 and TH01) and the Amelogenin marker. The detection of the Y allele in samples could provide a useful tool in the triage and submission of sexual assault samples by enforcement authorities. Male template material was detected on a range of common sexual assault evidence items including cotton pillow cases, condoms, swab heads and glass surfaces and shows a detection limit of 1 in 1000 dilution of neat semen. These data indicate this technology has the potential to be a useful tool for the detection of male donor DNA in sexual assault casework.