The effect of necrophagous entomofauna on textile damage during the summer in Western Australia

S. Ziogos; K. Pitts; I.R. Dadour; P.A. Magni

Learning Overview: After attending this presentation, attendees will have a better understanding of the impact and the artifacts produced by the activity of necrophagous entomofauna on stab-cuts and tear damage on different types of fabric during the postmortem period. Impact Statement: This presentation will impact the forensic science community by increasing awareness of the effect of carrion insects on clothing and by providing a new body of information that will enhance the investigative role of clothing associated with decomposed and skeletonized remains. Fatal stabbing incidents are the leading cause of homicides in countries with restricted access to firearms, such as Australia.1 During a stabbing assault, the distinctive characteristics of a sharp implement will deposit specific features.2 When the decomposition process impedes the physical examination of a stab wound, damage analysis of the clothing may provide information about the weapon or the actions that caused the injury.3 Studies have suggested that insect activity associated with decomposition can produce artifacts on textiles, modify perimortem textile damage or produce changes to clothing that imitate indicators of sexual homicides.4-7 However, the extent of such studies is currently limited and have not been conducted in Australia before. The aim of this research was to identify and characterize the effect of carrion insects on textile damage after a decomposition period during summer in Australia. The effect of insect activity was analyzed on standardized cuts and tears to three different fabrics (100% cotton, 65% polyester-35% cotton, 80% nylon- 20% spandex). Ninety stillborn piglets (Sus scrofa domesticus L.) were wrapped in one type of fabric each. Each clothed piglet was either stabbed by a stabbing apparatus or had its fabric torn. All piglets were placed simultaneously in a decomposition facility alongside controls of each combination of fabric and damage type, including 9 piglets clothed and intact; 6 piglets unclothed and stabbed or intact; 11 piglets enclosed in boxes; 36 field swatches; and 9 laboratory swatches. Over five sampling periods and until complete skeletonization (7, 12, 18, 26, 47 days since placement), 3 piglets of each type were removed, and entomological samples were collected. The fabric of each piglet was removed, photographed, and stored to dry in laboratory conditions before being analyzed. All controls and fabric swatches were collected on the final sampling day. Data collection was comprehensive of piglet and fabric samples via field assessment, daily photo and video documentation, static camera recording, and direct collection of insect specimens. Analyses performed covered taphonomic aspects (degree of piglet decomposition), entomological (insect species and instar), and textile damage analysis. The collected fabrics were analyzed on different levels of fabric structure using a stereoscope and digital microscope and through photo and video analysis. Fibers of each sample type were collected and examined using optical microscopy and Scanning Electron Microscopy (SEM). The results of this research show that stab cuts can adopt morphological characteristics over time that may resemble features of tear damage, whereas tear characteristics also tend to fade gradually. Insect interaction with bloodstains resulted in a distortion of the yarns and of the fabric surface after fly feeding. Due to the weakening of the fabric’s structure, insect damage and consequent degradation may occur at the same location. The assessment and comparison of fabrics revealed how parameters such as the type of fabric and elasticity can influence insect damage, with natural fabrics being the most vulnerable. Lastly, this research emphasizes how the presence and the type of fabrics and textile damage affect the interaction of carrion insects with the decomposing medium, and consequently, how the rate of decomposition in a natural environment and in confined spaces is affected.

The effect of necrophagous entomofauna on textile damage during the summer in Western Australia

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