DNA profiles generated from a range of touched sample types.

Direct PCR from touch DNA has a range of potential applications in the field of forensic investigation for exhibit examination that, under standard extraction methods, rarely produce informative DNA profiles. Previous studies from 'touch DNA' have focussed on fingermarks created under laboratory conditions. Here we report on successful STR DNA profiling from a range of touched items. Direct PCR, with no increase in cycle number, was performed after eight different sample types, typical of those submitted for forensic investigation, were handled by volunteers for a maximum of 15 s to deposit trace amounts of their DNA. Amplifications were performed using either GlobalFiler® or Identifiler® Plus following manufacturer's instructions. These two kits were chosen deliberately as many laboratories worldwide have adopted and validated them in their workflow, thus allowing for direct PCR to be incorporated within their practises easily. It was found that informative STR profiles were obtained from all eight substrates using both STR kits. Identifiler® Plus out-performed GlobalFiler® in terms of the percentage of alleles amplified using the direct PCR approach. Both generated informative profiles from all items and all individuals, at different rates, with Identifiler® Plus being informative in a larger percentage of samples. GlobalFiler® produced profiles with an average of 60% ±â€¯24% (36 ±â€¯15 alleles) alleles present while Identifiler® Plus produced profiles with an average of 96% ±â€¯4% (31 ±â€¯1 alleles) alleles present. A comparison was made between the direct PCR approach and subjecting touched samples to a standard DNA extraction process, both using Identifiler®. An average of 4% of profiles were informative for samples that underwent extraction with 100% being informative from the same subset of samples amplified by direct PCR. Our findings further demonstrate the success of direct PCR to enhance the STR DNA profiles from touch DNA. Further, Identifiler® Plus was found to generate informative profiles more often than GlobalFiler®. Direct PCR is fast, simple, and non-destructive of evidence with the ability to generate informative genetic data where standard methods are likely to fail.

DNA profiles from clothing fibers using direct PCR.

We report on the successful use of direct PCR amplification of single fibers from items of worn clothing. Items of clothing were worn throughout the course of a day, with the individual commencing regular activities. Single fibers were taken from the cuff of the clothing at regular intervals and amplified directly. The same areas were subjected to tape-lifting, and also amplified directly for comparison. The NGM™ kit that amplifies 15 STR loci plus amelogenin was used. A total of 35 single fiber samples were processed and analyzed from five items of clothing, with 81 % of samples returning a profile of 14 alleles or more. All tape-lift samples amplified directly produced DNA profiles of 15 alleles or more. The aim was to develop a simple, operational method that could be used routinely in forensic science casework and that has the potential to generate more complete profiles, which would not be detected using standard extraction methods on this type of sample. For ease of implementation, the process also adheres to standard methods with no increase in the cycle number.

Successful direct amplification of nuclear markers from single dog hairs using DogFiler multiplex.

We report on successful amplification of canine STR DNA profiles from single dog hairs. Dog hairs are commonly found on clothing or items of interest in forensic casework and may be crucial associative evidence if linked to an individual dog. We used direct amplification from these hairs to increase the DNA yield of the sample, as well as greatly reducing analysis time. Hairs from different somatic regions were used from several different dog breeds to amplify a selection of eight loci from the validated DogFiler multiplex. Naturally shed canine hairs were processed, with a mix of coarse topcoat (guard) hairs and thinner soft undercoat hairs. Multiple sections of single hairs were amplified in 5 mm segments to determine the viability of DNA recovery from the shaft of the hair. Single guard hairs were cut into 5 mm sections and added directly into a PCR tube. Undercoat hairs, which are very fine, were amplified together in a single tube (approximately ten small hairs). Coarse hairs were found to be the most successful in producing full DNA profiles at all eight loci, matching the corresponding reference profile for that dog.