Validation of presumptive tests for non-human blood using Kastle Meyer and Hemastix reagents.

Kastle Meyer and Hemastix reagents are presumptive tests commonly used in forensic casework for the detection of blood, and their suitability has been reviewed in numerous publications. However, studies to date have focused on the validation of these tests on human blood alone, and no published work has looked at the sensitivity, specificity and effect on DNA analysis when using these reagents to presumptively test for animal blood. The aim of this study was to validate the two reagents for use with animal blood, and compare their performance in order to choose the best test based on the circumstances in wildlife crime investigation. The sensitivity, specificity, stability and robustness of the methods were assessed by experiments with dilutions of animal blood (from 1:4 to 1:65536) using direct and indirect (rub) tests, potential interfering substances, blood sources from different species and aged blood. The effects of the two reagents on subsequent DNA analysis were also investigated. During the direct tests, Kastle Meyer showed a higher sensitivity, detecting blood down to a dilution of 1:16,384, one order of magnitude lower than Hemastix. However during the rub test, Hemastix showed a higher sensitivity, detecting blood down to a dilution of 1:64 on porous materials while Kastle Meyer was positive only down to a dilution of 1:16. Moreover, when using the same swab for presumptive testing and DNA extraction, Hemastix testing allowed amplification of a sufficient amount of DNA for species identification at its limit of sensitivity on porous materials (1:64) while Kastle Meyer inhibited most amplification of DNA at its less sensitive limit of 1:16 dilution. On the other hand, Hemastix showed a much lower specificity, producing false positive results when exposed to tomato, potato, rust, avian uric acid, bleach and sink rot, while Kastle Meyer only produced a faint positive reaction from potato. Both tests performed equally well detecting fresh blood of different animal species. The stability test gave comparable results among the tests except for aged fish blood stains, where the Kastle Meyer test performed poorly. Owing to its ease of use, higher sensitivity, and lack of interference with downstream DNA analysis, and despite its reduced specificity compared to Kastle Meyer, the Hemastix method is more appropriate for use in wildlife crime investigations. Positive results would always be confirmed with DNA analysis and the low interference of the reagent will allow the use of a single swab for presumptive testing and DNA sampling.

Profiling in wildlife crime: Recovery of human DNA deposited outside.

Incidents of bird of prey persecution receive a lot of media coverage in the UK, with investigations rarely recovering sufficient evidence to proceed to prosecution. One of the main challenges is to identify a suspect, as these offences are carried out in remote locations without witnesses, and crime scenes may not be found for days. However, traps, poisoned baits and bird of prey carcasses can be recovered from these crime scenes. This study aimed to determine whether reportable human DNA profiles could be recovered from any of these substrates after periods of time outside. Experiments depositing human touch DNA on duplicate substrates (traps, rabbit baits and corvid carcasses) set for 0, 1, 2, 4, 7 and 10 days outside were carried out, with DNA recovery and profiling following standard operating procedures for Scottish Police Authority Forensic Services. Weather conditions varied among experiments, including some heavy rainfall. Results demonstrated that it was possible to obtain reportable DNA profiles from all substrates after at least 1 day outside. Most promisingly, the traps showed no drop-off in DNA persistence over the experiments as complete DNA profiles were obtained after the full 10 days outside. A further experiment using 4 bird of prey carcasses confirmed that it is possible to obtain reportable human DNA profiles from them after 1 day outside (n = 2 reportable profiles). These results show that touch DNA can persist in an outdoor environment, and provide a tantalising avenue for inquiry in bird of prey persecution investigations.

Blood splash injury: an underestimated risk in endourology.

BACKGROUND AND PURPOSE: Mucocutaneous and transconjunctival exposure are important portals for the transmission of blood-borne infections to surgeons and health-care workers. Despite this knowledge, few surgeons or their assistants wear protective equipment for procedures perceived to be affiliated with less risk. This study investigates the potential risk of mucocutaneous and transconjunctival blood splash injury during common laparoscopic and endourologic procedures undertaken using standard video endoscopy equipment. MATERIAL AND METHODS: Masks combined with eye shields were consecutively collected from the surgeon, surgical assistant, and theater nurse after a variety of endourologic procedures over a 4-month period. These were analyzed macroscopically for visible blood droplets. Modern forensic techniques were then instituted to assess for nonvisible blood exposure. RESULTS: Eye shields from 118 procedures performed by five surgeons were collected. Two hundred and thirty-six masks were examined for visible and visually enhanced evidence of blood contamination. In total, 48.5% of surgeons' masks, 29.5% of assisting surgeons' masks, and 31.8% of scrub nurse masks were positive for either visible or visually enhanced blood contamination. In terms of evidence of blood splash, 84.2% of laparoscopic nephrectomies, 66.7% of pyeloplasties, and 58.3% of flexible ureteroscopies tested positive. CONCLUSION: Splash injuries remain commonplace, even with the use of video endoscopy equipment. Therefore, all health-care workers should be encouraged to wear eye and face protection when undertaking both endoscopic and laparoscopic urologic procedures. These observations may have broader implications relevant to all minimally invasive surgical procedures, because they demonstrate a much greater potential risk of blood-borne disease transmission during surgery than has been previously appreciated.