Estimating the postmortem interval (PMI) is one of the major tasks and a continuous challenge in forensic pathology. It is often an exclusion process of available methods, which ultimately can lead to an unsatisfactory outcome due to poor reliability. This problem is most acute in the late PMI, when decomposition proceeds and some methods (such as rigor, livor, and algor mortis) are no longer applicable. Several methods, such as forensic entomology, skeletal muscle protein degradation, and the study of body decomposition by application of a morphological scoring, are expected to provide further information; however, all have certain limitations and weaknesses. Availability of a toolbox of methods allows a case-specific selection of the most appropriate one(s), or eventually provides improvements in the overall accuracy and precision of the PMI estimation by merging and combining methods. To investigate practical (field) application, eventual interferences, and/or synergetic effects, as well as the robustness of these methods towards specific influencing factors, a field study was conducted, using eight pig cadavers of different body weights and physical coverage, left to decompose under natural conditions for 16 days. Morphological changes during decomposition were assessed using the total body score (TBS), muscle samples were collected to analyze protein degradation, and insect colonization was evaluated. The results reveal strengths and current limitations of all tested methods, as well as promising synergistic effects, and thus, provide a baseline for targeted future research.

Eight cases that occurred indoors in which the insects played an important role in the mPMI estimation are presented. The bodies of socially isolated people and old people living alone were discovered in central Italy between June and November. mPMI ranged from a few days to several weeks. Insects were collected during the body recovery and the postmortem. Climatic data were obtained from the closest meteorological stations and from measurements performed on the site. Sarcophagidae and Calliphoridae species were present in 75% of the cases with Lucilia sericata and Chrysomya albiceps collected in 50% of the cases. Chrysomya albiceps was always found in association with Lucilia species. Scuttle flies (Phoridae) were found in 37.5% of the cases, confirming the ability of these species in indoor body colonization. We show that if sealed environment may delay, the insect arrival dirty houses may create the environment where sarcosaprophagous insects are already present.

Hanging is one of the most common methods of suicide worldwide. Despite the high incidence, only a little knowledge about the pattern of cadaver colonization by insects on hanging corpse is available. Different types of hanging can alter the body decomposition process as well as the pattern and rate of insect colonization. Two case studies where the hanging occurred with a similar postmortem interval of 34 days are described. The two bodies showed different patterns of insect colonization and decomposition scored using the Total Body Score (TBS) and the TBS for hanging (TBShang). The first case was about the body of a 24-years-old male, with mummification of the unclothed upper anatomical parts. A TBS of 14 and a TBShang of 18 were assigned. The second body, belonging to a 15-years-old male, was found pre-skeletonized lying on the ground with the skull disarticulated. A TBS of 31 and a TBShang of 32 were assigned. Average temperatures of (21.5 ± 2.5) °C for the first body and (25.1 ± 2.7) °C for the second body were recorded in the 34 days preceding the bodies’ discovery for a total of 731 and 853 Accumulated Degree Days (ADD) respectively. According to previous studies, the different decomposition patterns were related to temperatures of exposition and to the diversity of arthropod community found on the bodies because of the different types of hanging: totally suspended vs. in contact with the soil. The limited insect activity caused by hanging explains the delay in decomposition of hanging bodies in which mummification can take place, especially on the upper body parts. In vertical body position, the body fluids accumulated in the lower body parts accelerating the desiccation of soft tissues on the upper parts. The effect of gravity can also explain the decrease of internal maggot mass as larvae easily fall from the hanging body to the drip zones below where they are unable to recolonize the body if totally suspended. Furthermore, in a hanging body a greater surface is exposed to wind and sun with a quicker skin drying preventing the additional Diptera colonization. This paper shows the weaknesses of scoring scales and regression models developed to predict ADD when irregular decomposition and mummification have not taken into account.

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