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Profiling the scent of weathered training aids for blood-detection dogs
Authors:Baree Chilcote  LaTara Rust  Katie D Nizio  Shari L Forbes
Institution:University of Technology Sydney, Centre for Forensic Science, P.O. Box 123, Broadway, NSW 2007, Australia
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.
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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