Chilcote Baree, Rust LaTara, Nizio Katie D, Forbes Shari L
University of Technology Sydney, Centre for Forensic Science, P.O. Box 123, Broadway, NSW 2007, Australia.
Sci Justice. 2018 Mar;58(2):98-108. doi: 10.1016/j.scijus.2017.11.006. Epub 2017 Nov 23.
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.
在室外犯罪现场，尸体探测犬和血迹探测犬可能被要求寻找已存在数天、数周或数月的血迹。虽然已知血迹的气味特征在此期间会发生变化，但目前尚不清楚暴露在环境中时其特征是如何变化的。必须研究这些变量，以便了解何时血迹探测犬无法再检测到气味特征，以及应何时使用其他犯罪现场工具。在本研究中，将血液滴落在混凝土和涂漆木质表面上，并在室外环境中风化三个月。使用固相微萃取（SPME）收集顶空样品，并使用全二维气相色谱-飞行时间质谱（GC×GC-TOFMS）进行分析。将化学气味特征与尸体探测犬和血迹探测犬在训练期间的行为反应进行比较。使用主成分分析（PCA）和层次聚类分析（HCA）进行数据解释，结果表明，在两个表面上风化两个月后，使用SPME-GC×GC-TOFMS无法再检测到血液气味。相反，血迹探测犬在混凝土表面风化一个月后以及在涂漆木质表面风化一周后，很难找到血样。本文评估的气味探测犬在训练期间此前未接触过经环境风化的血样。鉴于本研究旨在测试犬的基线能力，预计通过反复接触，犬的能力可能会提高。从本研究中获得的知识有助于为执法部门提供更准确的血迹探测犬训练辅助工具，并提高它们在部署到室外犯罪现场时的效率。
