Estimation of postmortem interval in decomposed remains using insect evidence: A report of two cases

Accurate postmortem interval (PMI) estimation is crucial in forensic cases. Forensic entomology, analyzing insect species, developmental stages, and environmental factors associated with decomposing remains, has proved to be an effective method for estimating extended PMIs, especially when traditional postmortem indicators are no longer viable. This study presents two cases demonstrating how to estimate the minimum postmortem interval (PMI_min) by integrating seasonal insect activity, developmental anomalies, and environmental factors. In Case 1, the body was discovered in early spring under low-temperature conditions. However, empty puparia of Chrysomya megacephala (Fabricius, 1794) and Chrysomya rufifacies (Macquart, 1844) were found on the corpse, indicating that the death occurred during warm weather. Additionally, the presence of developmentally abnormal pupae suggests that the insects may have been exposed to extreme weather, such as a sudden drop in temperature. Based on these observations, the PMI_min was estimated to be in late summer or early autumn of the previous year. Similarly, limited insect evidence on the remains, combined with local climatic data, supported an estimated PMI_min in early autumn of the previous year for Case 2. These findings highlight the significant influence of seasonal insect activity and environmental factors on insect development and distribution, providing critical insights for estimating longer PMIs. This study emphasizes forensic investigations should consider species-specific seasonal and geographical distribution patterns, as well as the environmental adaptability of insects. Moreover, given global climate change and resultant species migration, continuous insect succession experiments are essential for updating forensic entomological databases and improving their practical applicability.