Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Department of Oral Sciences, University of Otago, Dunedin, New Zealand.
Int J Legal Med. 2023 Nov;137(6):1897-1906. doi: 10.1007/s00414-023-03068-0. Epub 2023 Aug 16.
Time since death estimation is a vital part of forensic pathology. Despite the known tissue degradation after death, the efficacy of using biomechanical tissue properties to estimate time since death remains unexplored. Here, eight brain tissue localizations were sampled from the frontal lobe, parietal lobe, anterior and posterior deep brain, superior colliculi, pons, medulla, and cerebellum of 30 sheep; were then stored at 20 °C; and subsequently subjected to rheometry tests on days zero to four after death. Overall, the measured tissue storage modulus, loss modulus, and complex shear modulus decreased after death for all of the tested regions in a site-specific manner. Day zero to day one changes were the only 24-h interval, for which statistically significant differences in tissue mechanical moduli were observed for some of the tested brain regions. Based on receiver operator characteristic analyses between day zero and the pooled data of days one to four, a post mortem interval of at least 1 day can be determined with a sensitivity of 90%, a specificity of 92%, and a positive likelihood ratio of 10.8 using a complex shear modulus cut-off value of 1461 Pa for cerebellar samples. In summary, biomechanical properties of brain tissue can discriminate between fresh and at least 1-day-old samples stored at 20 °C with high diagnostic accuracy. This supports the possible value of biomechanical analyses for forensic time since death estimations. A striking advantage over established methods to estimate the time since death is its usability in cases of disintegrated bodies, e.g. when just the head is found.
死亡时间推断是法医病理学的重要组成部分。尽管已知死后组织会降解，但使用生物力学组织特性来推断死亡时间的效果仍未得到探索。在这里，从 30 只绵羊的额叶、顶叶、前脑和后脑深部、上丘、脑桥、延髓和小脑的 8 个脑组织定位部位采集样本；然后将其储存在 20°C；随后在死后零天至四天进行流变学测试。总体而言，所有测试区域的组织储存模量、损耗模量和复剪切模量在死后均呈特定部位的方式下降。只有在 0 天到 1 天的变化是唯一一个 24 小时的间隔，在这个间隔内，一些测试的大脑区域的组织力学模量有统计学上的显著差异。基于 0 天与 1 天至 4 天的汇总数据之间的接受者操作特征分析，使用小脑样本的 1461 Pa 复剪切模量截断值，可以确定至少 1 天的死后间隔时间，其灵敏度为 90%，特异性为 92%，阳性似然比为 10.8。总之，脑组织的生物力学特性可以区分在 20°C 下储存的新鲜和至少 1 天的样本，具有很高的诊断准确性。这支持了生物力学分析在法医死亡时间推断中的潜在价值。与用于估计死亡时间的既定方法相比，它的一个显著优势是其在尸体分解的情况下，例如只有头部被发现时，仍然可用。
