Cockle Diane Lyn, Bell Lynne S
Archaeology Department, Forensic Research Centre Simon Fraser University 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
School of Criminology, Forensic Research Centre Simon Fraser University 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
Sci Justice. 2017 Mar;57(2):107-117. doi: 10.1016/j.scijus.2016.11.001. Epub 2016 Nov 5.
Little is known about the nature and trajectory of human decomposition in Canada. This study involved the examination of 96 retrospective police death investigation cases selected using the Canadian ViCLAS (Violent Crime Linkage Analysis System) and sudden death police databases. A classification system was designed and applied based on the latest visible stages of autolysis (stages 1-2), putrefaction (3-5) and skeletonisation (6-8) observed. The analysis of the progression of decomposition using time (Post Mortem Interval (PMI) in days) and temperature accumulated-degree-days (ADD) score found considerable variability during the putrefaction and skeletonisation phases, with poor predictability noted after stage 5 (post bloat). The visible progression of decomposition outdoors was characterized by a brown to black discolouration at stage 5 and remnant desiccated black tissue at stage 7. No bodies were totally skeletonised in under one year. Mummification of tissue was rare with earlier onset in winter as opposed to summer, considered likely due to lower seasonal humidity. It was found that neither ADD nor the PMI were significant dependent variables for the decomposition score with correlations of 53% for temperature and 41% for time. It took almost twice as much time and 1.5 times more temperature (ADD) for the set of cases exposed to cold and freezing temperatures (4°C or less) to reach putrefaction compared to the warm group. The amount of precipitation and/or clothing had a negligible impact on the advancement of decomposition, whereas the lack of sun exposure (full shade) had a small positive effect. This study found that the poor predictability of onset and the duration of late stage decomposition, combined with our limited understanding of the full range of variables which influence the speed of decomposition, makes PMI estimations for exposed terrestrial cases in Canada unreliable, but also calls in question PMI estimations elsewhere.
在加拿大，人们对人体分解的性质和过程知之甚少。本研究对96例回顾性警方死亡调查案件进行了检查，这些案件是从加拿大暴力犯罪关联分析系统（ViCLAS）和警方猝死数据库中选取的。基于观察到的自溶（1 - 2期）、腐败（3 - 5期）和白骨化（6 - 8期）的最新可见阶段，设计并应用了一个分类系统。利用时间（死后间隔时间（PMI），以天为单位）和温度累积度日（ADD）得分对分解过程进行分析，发现在腐败和白骨化阶段存在相当大的变异性，在第5阶段（腹胀后）之后预测性较差。户外分解的可见过程在第5阶段的特征是从棕色变为黑色，在第7阶段是残余的干燥黑色组织。没有尸体在一年内完全白骨化。组织木乃伊化很少见，冬季比夏季更早出现，认为这可能是由于季节性湿度较低。研究发现，ADD和PMI都不是分解得分的显著因变量，温度的相关性为53%，时间的相关性为41%。与温暖组相比，暴露在寒冷和冰冻温度（4°C或更低）下的一组案例达到腐败所需的时间几乎是其两倍，温度（ADD）则多1.5倍。降水量和/或衣物对分解进程的影响可忽略不计，而缺乏阳光照射（完全遮荫）有较小的积极影响。本研究发现，后期分解的起始和持续时间预测性较差，再加上我们对影响分解速度的所有变量的了解有限，使得加拿大暴露在陆地上的案例的PMI估计不可靠，同时也对其他地方的PMI估计提出了质疑。
