Giles Stephanie B, Errickson David, Márquez-Grant Nicholas
Cranfield Forensic Institute, Cranfield Defence and Security (CDS), Cranfield University, Shrivenham, Swindon SN6 8LA, United Kingdom.
Cranfield Forensic Institute, Cranfield Defence and Security (CDS), Cranfield University, Shrivenham, Swindon SN6 8LA, United Kingdom.
Sci Justice. 2022 Mar;62(2):246-261. doi: 10.1016/j.scijus.2022.02.003. Epub 2022 Feb 9.
Post-mortem interval (PMI) information sources may be subject to varying degrees of reliability that could impact the level of confidence associated with PMI estimations in forensic taphonomy research and in the practice of medico-legal death investigation. This study aimed to assess the reliability of PMI information sources in a retrospective comparative analysis of 1813 cases of decomposition from the Allegheny County Office of the Medical Examiner in Pittsburgh, US (n = 1714), and the Crime Scene Investigation department at Southwest Forensics in the UK (n = 99). PMI information sources were subjected to a two-stage evaluation using an adapted version of the 3x5 aspects of the UK police National Intelligence Model (NIM) to determine the confidence level associated with each source. Normal distribution plots were created to show the distribution frequency of the dependent variables (decomposition stage and source evaluation) by the independent variable of PMI. The manner, location, and season of death were recorded to ascertain if these variables influenced the reliability of the PMI. A confidence matrix was then created to assess the overall reliability and provenance of each PMI information source. Reliable PMI sources (including forensic specialists, missing persons reports, and digital evidence) were used across extensive PMI ranges (1 to 2920 days in the US, and 1 to 240 days in the UK) but conferred a low incidence of use with forensic specialists providing a PMI estimation in only 35% of all homicide cases. Medium confidence PMI sources (e.g., last known social contact) accounted for the majority of UK (54%, n = 54) and US (82%, n = 1413) cases and were associated with shorter PMIs and natural causes of death. Low confidence PMI sources represented the lowest frequencies of UK and US cases and exclusively comprised PMI information from scene evidence. In 96% of all cases, only one PMI source was reported, meaning PMI source corroboration was overall very low (4%). This research has important application for studies using police reports of PMI information to validate PMI estimation models, and in the practice of medico-legal death investigation where it is recommended that i) the identified reliable PMI sources are sought ii) untested or unreliable PMI sources are substantiated with corroborating PMI information, iii) all PMI sources are reported with an associated degree of confidence that encapsulates the uncertainty of the originating source.
死后间隔时间（PMI）的信息来源可能具有不同程度的可靠性，这可能会影响法医尸理学研究和法医学死亡调查实践中与PMI估计相关的置信水平。本研究旨在通过对美国匹兹堡阿勒格尼县法医办公室1813例尸体分解案例（n = 1714）以及英国西南法医科学中心犯罪现场调查部门99例案例进行回顾性比较分析，评估PMI信息来源的可靠性。使用英国警方国家情报模型（NIM）3×5方面的改编版本对PMI信息来源进行两阶段评估，以确定与每个来源相关的置信水平。创建正态分布图以显示由PMI自变量引起的因变量（分解阶段和来源评估）的分布频率。记录死亡方式、地点和季节，以确定这些变量是否会影响PMI的可靠性。然后创建一个置信矩阵，以评估每个PMI信息来源的整体可靠性和出处。可靠的PMI来源（包括法医专家、失踪人员报告和数字证据）在广泛的PMI范围内使用（美国为1至2920天，英国为1至240天），但法医专家在所有凶杀案中仅在35%的案件中提供PMI估计，使用率较低。中等置信度的PMI来源（例如，最后已知的社会接触）在英国（54%，n = 54）和美国（82%，n = 1413）的案例中占大多数，并且与较短的PMI和自然死亡原因相关。低置信度的PMI来源在英国和美国案例中出现频率最低，仅包括来自现场证据中的PMI信息。在所有案例的96%中，仅报告了一个PMI来源，这意味着PMI来源的相互印证总体非常低（4%）。本研究对于使用PMI信息警方报告来验证PMI估计模型的研究具有重要应用价值，并且在法医学死亡调查实践中，建议：i）寻找已确定的可靠PMI来源；ii）用相互印证的PMI信息证实未经检验或不可靠的PMI来源；iii）报告所有PMI来源时应附上相关置信度，该置信度应涵盖原始来源的不确定性。
