Profiling the scent of weathered training aids for blood-detection dogs |
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Authors: | Baree Chilcote LaTara Rust Katie D Nizio Shari L Forbes |
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Institution: | University of Technology Sydney, Centre for Forensic Science, P.O. Box 123, Broadway, NSW 2007, Australia |
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Abstract: | At outdoor crime scenes, cadaver-detection and blood-detection dogs may be tasked with locating blood that is days, weeks or months old. Although it is known that the odour profile of blood will change during this time, it is currently unknown how the profile changes when exposed to the environment. Such variables must be studied in order to understand when the odour profile is no longer detectable by the scent-detection dogs and other crime scene tools should be implemented. In this study, blood was deposited onto concrete and varnished wood surfaces and weathered in an outdoor environment over a three-month period. Headspace samples were collected using solid phase microextraction (SPME) and analysed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC–TOFMS). The chemical odour profiles were compared with the behavioural responses of cadaver-detection and blood-detection dogs during training. Data interpretation using principal component analysis (PCA) and hierarchical cluster analysis (HCA) established that the blood odour could no longer be detected using SPME–GC×GC–TOFMS after two months of weathering on both surfaces. Conversely, the blood-detection dogs had difficulty locating the blood samples after one month of weathering on concrete and after one week of weathering on varnished wood. The scent-detection dogs evaluated herein had not been previously exposed to environmentally weathered blood samples during training. Given that this study was conducted to test the dogs' baseline abilities, it is expected that with repeated exposure, the dogs' capabilities would likely improve. The knowledge gained from this study can assist in providing law enforcement with more accurate training aids for blood-detection dogs and can improve their efficiency when deployed to outdoor crime scenes. |
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Keywords: | BOM Bureau of Meteorology EDTA ethylenediaminetetraacetic acid crit critical value PC-1 first principal component GC–MS gas chromatography – mass spectrometry GC×GC–TOFMS comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry HCA hierarchical cluster analysis 3 tripotassium ethylenediaminetetraacetic acid NIST National Institute of Standards and Technology PCA principal component analysis PDMS/DVB polydimethylsiloxane/divinylbenzene RSID?- Blood Rapid Stain Identification of Human Blood S/N signal-to-noise ratio (PC-2) second principal component SPME solid phase microextraction TIC total ion current VOCs volatile organic compounds Blood Weathering SPME GC×GC-TOFMS VOCs Blood-detection dogs |
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