Characterising chemical markers of decomposition to advance death investigations

分解化学是一个新兴的法医学领域，研究身体在死后的降解途径。软组织的生化降解包括细胞的解体和脂肪、蛋白质、碳水化合物和核酸产物向环境的释放。随着时间的推移，使用先进的色谱和光谱技术对这些副产品进行分析，有可能确定与死后时期相关的新的有机标记。执法部门和法医部门可利用这些信息进行死亡调查，并改进搜索和找回技术(如身体犬)的培训。然而，目前这些方法在加拿大环境中的应用是不可能的，因为化学数据只使用猪的身体收集，而且最近的研究表明，它们不能直接与人类身体相比较。由于气候和生物地理的根本差异，利用美国和澳大利亚较温和地区的身体进行的研究不适用于加拿大环境。*这项研究旨在描述软组织分解过程中发生的独特化学变化，并确定加拿大东部气候对软组织腐烂速度和过程的影响。研究将在死因研究安全地点(SSRT)进行，这是加拿大唯一使用捐赠身体研究人类分解的设施。在SSRT收集的有机样品将使用全面的二维气相色谱飞行时间质谱仪进行分析，这是分离和鉴定复杂分解产物的唯一具有足够分辨率的仪器。该计划包括系统地收集空气和土壤中的挥发性有机化合物(VOC)，以开发一个全面的分解气味数据库。该数据库将被用来发现身体狗在寒冷气候下用来定位受害者遗骸的关键VOCs。将收集组织、土壤和纺织品的样本，以提取和识别与尸检时间相关的腐烂化学标记。这些标记的特征将允许更准确地估计自身体死亡或沉积以来的时间。*这项研究将改变我们对加拿大身体狗如何定位腐烂气味的理解，并将用于改进它们在定位受害者遗骸方面的培训和成功。识别新的分解标记对于向执法部门提供准确的时间范围至关重要，并将通过缩小相关失踪人员记录来帮助确认受害者身份。从这个项目中获得的基础知识将为分解化学研究社区设定一个全球标准。这一结果对加拿大的执法部门和受害者家属都有明显的好处，并通过迅速查明和遣返战争罪或大规模灾难的受害者而对全球产生影响。

Decomposition chemistry is an emerging field of forensic science that studies the degradation pathways in a body postmortem. The biochemical degradation of soft tissue involves the disintegration of cells and the release of lipid, protein, carbohydrate, and nucleic acid products to the environment. Analysis of these by-products using advanced chromatographic and spectroscopic techniques over time has the potential to identify novel organic markers that correlate with the postmortem period. This information can be used by law enforcement and forensic services in death investigations, and to improve training in search and recovery techniques (e.g. cadaver dogs). However, current application of these methods in Canadian environments is not possible as chemical data has only been collected using pig carcasses, and recent research has shown that they are not directly comparable to human cadavers. Studies that have utilised cadavers in milder regions of the USA and Australia cannot be applied to Canadian environments due to fundamental differences in climate and biogeography. ******This research aims to characterize the unique chemical changes that occur during soft tissue decomposition and to determine the impact of the eastern Canadian climate on the rate and process of decay. Research will be conducted at the Secure Site for Research in Thanatology (SSRT), the only facility in Canada for the study of human decomposition using donated cadavers. Organic samples collected at SSRT will be analysed using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry, the only instrument with sufficient resolution to separate and identify the complex products of decomposition. The program involves the systematic collection of volatile organic compounds (VOC) from air and soil to develop a comprehensive decomposition odour database. The database will be used to discover the key VOCs used by cadaver dogs for locating victim remains in a cold climate. Samples of tissue, soil and textiles will be collected to extract and identify chemical markers of decomposition that correlate with the postmortem period. Characterisation of these markers will allow for more accurate estimations of time since death or deposition of a body. ******The research will change our understanding of how cadaver dogs locate decomposition odour in Canada and will be used to improve their training and success in locating victim remains. Identification of novel decomposition markers are essential for providing accurate timeframes to law enforcement and will aid victim identification by narrowing pertinent missing persons records. The fundamental knowledge gained from this program will set a global standard for the decomposition chemistry research community. The outcomes have a clear benefit to both law enforcement and families of victims in Canada, as well as global implications through the rapid identification and repatriation of victims of war crimes or mass disasters.