Decomposition pattern and insect colonization in two cases of suicide by hanging

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 (TBS_hang). 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 TBS_hang 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 TBS_hang 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.