The suitability of visual decomposition scoring systems for estimating post-mortem submersion interval: a human skin tone and weather perspective

The estimation of Post-Mortem Interval (PMI) remains a global challenge, but the estimation of Post-Mortem Submersion Interval (PMSI) in cases of drowning or those submerged from aquatic ecosystems is still particularly difficult. Decomposition Scoring Systems (DSS) are currently used to estimate PMSI for drowning cases. The most used DSS methods include the Heaton et al. (2010), van Daalen et al. (2017) and Reh (1967), which have been developed in temperate climates with predominantly lighter skin-toned populations. This posed the question, ‘Are these DSS useful for drowning cases involving individuals with darker skin tone?’ We aimed to validate whether current DSS are applicable to forensic cases involving individuals with darker skin tones who were recovered from water. Accurate estimates of the PMSI were assessed using the Heaton, van Daalen and Reh DSS to measure decomposition visible in photographs of 73 cases of bodies recovered from water compared with the stated PMSI in their case notes from the Netherlands, United Kingdom, and South Africa. The results showed that discolouration changes in skin can be misleading when using the current DSS for individuals with darker skin tone, and these DSS are erroneous for estimating the PMSI of individuals with darker or lighter skin tones in an advanced decomposition stage or those recovered in cold months. Therefore, current DSS are only applicable to cases with comparable climates and aquatic environments, but also to individuals with lighter skin tones. To improve the PMSI estimation, recommendations are provided to apply the current DSS to individuals with darker skin tones. Additionally, global studies are required to improve the suitability of current DSS to assess decomposition and estimate PMSI for individuals with darker skin tones.