Accuracy of estimating postmortem interval using the relationship between total body score and accumulated degree-days: a systematic review and meta-analysis

This study aims to evaluate the relationship between Total Body Score (TBS) and Accumulated Degree-Days (ADD) for estimating postmortem interval (PMI) using the decomposition quantification system by Megyesi et al. (Megyesi MS, Nawrocki SP, Haskell NH (2005) Using Accumulated Degree-Days to Estimate the Postmortem Interval from Decomposed Human Remains. J Forensic Sci 50:1–9. https://doi.org/10.1520/jfs2004017).

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The methodological quality and risk of bias were assessed using the QUADAS-2 scoring system. Statical tests, including I² for heterogeneity assessment and subgroup analysis comparing human and pig proxies across different decomposition stages, were performed for meta-analysis.

The search identified 25 studies that underwent qualitative evaluation, all of which were included for quantitative analysis. The findings indicate that the TBS formula tends to overestimate ADD with a moderate mean difference of 0.5758 overall. Specifically, in pigs, ADD is overestimated significantly (1.1128), while there is a slight underestimation in humans (-0.0038). Across decomposition stages, fresh body (0.0066) and early decomposition (0.0338) show an insignificant overestimation, whereas advanced decomposition reveals a slight underestimation (-0.3378) and skeletonization indicates a substantial overestimation (1.6583).

The relationship between TBS and ADD demonstrates high accuracy in humans during early decomposition stages, without differences in statistical significance. However, its accuracy diminishes as decomposition progresses, potentially leading to an overestimation of PMI.