Inter-operator reliability of the total decomposition score (TDS) method for estimating the post-mortem interval (PMI) in outdoor cases

In the estimation of the Post-Mortem Interval (PMI), semi-quantitative methods have been proposed to overcome the challenges associated with determining the time of death. Among these, the Total Decomposition Score (TDS) method, developed by Gelderman et al., offers a systematic and semi-quantitative approach for estimating PMI. The aim of this study was to evaluate the reliability of the TDS by assessing its interoperator variability and comparing the results obtained with known reference data. A TDS-based questionnaire was administered to 100 participants - including forensic pathologists, residents in forensic medicine and professionals in forensic thanatology - using a dataset of six outdoor cadavers representing different decomposition stages. Data were analyzed using Fleiss’ Kappa (K) to assess inter-rater agreement and Spearman’s rank correlation to evaluate consistency. The results showed moderate overall agreement, with inter-rater reliability decreasing in cases with PMI exceeding 30 days. Linear regression analyses between estimated and actual post-mortem intervals yielded low coefficients of determination, with R² = 34.1% for the TDS-based model and R² = 20.5% for the ADD-based model, indicating that both methods explain only a limited portion of the variance in the actual PMI (PMIa). No statistically significant differences were observed among the professional categories, supporting the method’s applicability across different levels of expertise. While TDS shows promise as a practical tool for PMI estimation in field conditions, inter-operator variability remains a limiting factor in advanced decomposition stages.