Fingernail evidence is often collected in criminal cases of violent and/or sexual assault. In acts of aggression and self-defense, foreign deoxyribonucleic acid (DNA) can be transferred from the perpetrator to beneath the surface of the fingernail of the victim. It is possible to recover this foreign, exogenous DNA from the victim’s fingernails and potentially identify the perpetrator via DNA analysis. When attempting to recover this DNA from fingernail clippings, a couple of problems can occur. Often times, not enough exogenous DNA gets trapped underneath fingernails, so there is not usually much DNA to work with for recovery. The other major problem is the presence of endogenous DNA from the fingernail donor. Not only is there donor DNA in the fingernail itself, but the donor’s own DNA can build up underneath their nails simply by rubbing their face or combing their fingers through their hair. This means that there can be more donor DNA present that can mask the presence of the foreign DNA and cloud the results. In an attempt to improve the recovery of foreign DNA and produce a reportable, informative profile, a time course study was developed. Typically, when using forensicGEM as an extraction method, the samples would incubate for 15 minutes before going through protease inactivation. For this study, the extraction period was broken up into four 5-minute periods of incubating, for a total of 20 minutes, before inactivating the protease. This was done to pinpoint the time period at which more foreign DNA is being extracted from the surface of the nail before endogenous DNA is extracted in excess and clouds or even hides the presence of foreign DNA altogether. Female fingernail clippings were spiked with neat male saliva to observe the ratio of male to female DNA during quantitation and on the electropherograms. The quantitation results depicted a strong presence of male DNA through the entirety of the time course, and female DNA did not appear to be extracted in greater levels until the 15 minutes of incubation. The resulting profiles exhibited the male saliva profile as the major contributor for most of the samples, especially at the 5- and 10-minute markers. In 50% of the profiles, a minor female contributor could be identified as the nail donor. One sample produced a single, male profile for each time point with no indication of a female donor present in the extract; another sample produced a profile with a male major contributor with only 3 to 6 loci having additional detectable alleles of a minor contributor at each time point. These alleles could not be conclusively attributed to the female nail donor, but she could not be excluded. These preliminary results indicate that a shortening of the forensicGEM extraction period could be beneficial for improving the recovery ratio of exogenous to endogenous DNA from fingernail evidence.

When offenders commit crime there is the potential that they may leave behind trace amounts of their DNA, even when there has been no apparent body fluid spill. During the examination of crime scenes, scene investigators try to identify areas that may be sampled to locate these traces. Specialist techniques are then required within the laboratory to enable such small amounts to be analysed to obtain a profile. These techniques are referred to as Low Template DNA analysis (LTDNA), of which Low Copy Number DNA (LCN DNA) is one instance. In 2008, following the Omagh Bombing trial, and comments made by Judge Weir, the UK Forensic Regulator commissioned a review of the science of LTDNA analysis. The subsequent report made specific mention of the fact that there was no available information on the success rate of the use of such DNA techniques and that there seemed to be confusion over what constituted a success. The report went on to state that there was no information on where such trace amounts of DNA were likely to be found, or what factors could influence the likelihood of obtaining a trace DNA profile (Caddy, 2008). This research considered the outcomes of LCN DNA analysis from 3,552 samples to try to establish where trace amounts of DNA could be found, whether some areas sampled were more successful in generating profiles than others, and the likelihood of the profiles obtained being of use to a criminal investigation. Analysis of results identified areas that were more successful in generating profiles of use to an investigation and highlighted significant differences in results across a variety of items from which samples were taken. DNA samples taken from items associated with communication such as mobile phones were much more likely to produce a profile useful to a criminal investigation than those taken from fixed surfaces within premises. The results obtained showed that obtaining a DNA profile did not necessarily correlate with the profile being of use to a criminal investigation. This was due to the fact that a large number of these profiles were anticipated eliminations from legitimate sources. Items that produced high numbers of profiles but were anticipated eliminations, and therefore of no value to an investigation, came from items associated with skin samples and clothing. The research went further to identify key factors that affected the profiling rates. Factors that had a positive influence on the ability to obtain a profile included: any area that had been in close proximity to saliva (direct contact was not required); samples that had been recovered from the inside of premises or vehicles and therefore protected from the elements; those that were dry; items that were of a porous nature; and those that had a rough texture. No differences were found between the actual surface materials (plastic, glass, wood, metal), as all showed a propensity to generate profiles. Other factors that were considered but proved to have no effect on the profiling rates included seasonal differences and whether the area targeted for sampling was clearly defined. Items that had had high contact with a victim, were recovered from outside or had been wet, all proved to be less useful to an nvestigation. A further finding of the research was that swabs that had been recovered and stored frozen appeared to deteriorate in their ability to profile. This was particularly notable if they were submitted later than 5 months after recovery. Items stored in dry conditions did not deteriorate in this way. Overall the research can be used to provide investigators with the knowledge of what areas of crime scenes are most likely to yield trace DNA material, the key factors that can affect the likelihood of obtaining a profile, and those areas that are more likely to produce profiles useful to criminal investigations.