Ian Dadour

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.

Learning Overview: After attending this presentation, attendees will understand the effect of carrion insects on fabrics during the postmortem period. In particular, attendees will understand those variables (e.g., the nature of the fabric [natural, synthetic, blended], the fabric’s elastic content [% in elastane], the type of initial damage [tear/penetration] that will most impact on how the fabric modifies during a decomposition event). Impact on the Forensic Science Community: This presentation will impact the forensic science community 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 predominantly in countries with restricted access to firearms, such as Australia. During a stabbing assault, the distinctive characteristics of an implement deposit specific features, typically assessed during wound examination by a pathologist and/or during a fabric damage assessment by a forensic scientist. When the decomposition process impedes the identification and evaluation of the type and extent of a stabbing wound, fabric damage analysis on the victim’s clothing may provide information about the implement or the actions that caused the injuries. However, studies have suggested that insect activity can modify the original cut (e.g., exacerbating the fraying of a fabric’s cut, especially the edges of the cut). Furthermore, insect activity and the progression of decomposition such as bloating have also been reported to produce changes to clothing that in some cases may mimic indicators of sexual homicides. At present, there is a paucity of research focused on the effect of insect activity on different fabrics and the modifications they cause throughout the process of decomposition. The aim of this study is to analyze the effects of the activity of the necrophagous entomofauna during a summer season in Western Australia on different types of fabric (natural, synthetic, blended—with different amount of elastin), type of damage (tear/penetration), and time since death/insect colonization. For this study, 117 piglets (Sus scrofa L.) were used. Four different fabrics were selected based on their type (natural/synthetic) and their percentage in elastin (0%, 50%, 100%): (1) cotton 100%; (2) polyester 100%; (3) cotton-elastane 50%–50%; and (4) spandex 100%. All fabrics were woven. Of the 117 piglets, 112 were wrapped from the neck down with one layer of each fabric type and in the same weave orientation. Five piglets were not clothed and were used as controls. Twenty-four wrapped piglets were stabbed twice, consecutively and at identical anatomical positions with a Philips-head screwdriver (pointed edge) and 24 with a kitchen knife (sharp edge) by utilizing a stabbing apparatus (for consistency and to maintain a similar amount of pressure when thrusting). The fabric of 24 wrapped piglets was torn twice at the same positions as the penetrated piglets. Twenty-four wrapped piglets were left undamaged and 17 wrapped piglets were excluded from insect activity to serve as controls. Also, 112 samples of fabrics that were not wrapped on piglets were placed at the field site along with the samples. The experiment took place in a eucalypt woodland on sandy soil in southwestern Australia. The environmental conditions were also documented. Data collection was comprehensive of piglets, fabrics sample (a total of 20 replicants every three days from the beginning of the experiment), and insect specimens (via direct collection and adhesive traps). At each sampling period, photos and videos were recorded. Analyses performed covered both taphonomic aspects (degree of piglets’ decomposition), entomological (insect species and instar), and physical evidence (fabric damage via stereomicroscope and Scanning Electron Microscopy [SEM]). The statistical analysis considered the different variables (e.g., time since death, insect activity, type of fabric, type of damage) and assisted in the generation of likelihood ratios for the interpretation of damage on the fabrics. This presentation will discuss the results of this experiment and its impact on postmortem interval assessments, as well as implications on fabric damage analysis.

Wingbeat frequency and harmonics are being used to successfully identify agricultural pests and disease vectors in the field. This method is a viable alternative for identifying the forensically important blow fly (Diptera: Calliphoridae). The use of morphometric features and DNA to identify blow flies is difficult, time consuming and expensive, and are complicated by changes in species distribution and the appearance of invasive and hybrid species. Blow flies are the first to colonise decomposing remains and are ubiquitous. They provide valuable evidence when calculating time since death, as the development of the blow fly is highly predictable when using temperature and experimental reference data for the correctly identified species. However, species misidentification results in significant errors in estimating the time since death, as different blow fly species often have different developmental times and life history traits. Wingbeat frequency is measured using an optical sensor to record light fluctuations produced by the wings of an insect partially blocking the light when it flies between a laser beam and a phototransistor array. These fluctuations are then analysed by a classification model built and trained using a machine learning algorithm to identify each specimen by species and sex. This method enables the unbiased identification of an adult blow fly species with a reportable potential rate of error. The adult blow fly is the most mobile stage of the life cycle, determining the species’ presence in a decomposing community, and the speed at which it arrives. However, its role has been largely overlooked with much of the research being focused on the larvae. Flying adult flies are also difficult to study due to their small size and speed. The use of wingbeat frequency data to track and identify blowflies in real time will enable the research of arrival patterns of adult blow flies and the factors that influence detection and acceptance of a site for oviposition, by using a staged crime scene involving decomposing remains. Preliminary testing of common species belonging to the Lucilia and Calliphora genera has so far produced noisy, yet promising classification data. It is believed that by adjusting the placement of the sensor, a smoother signal will be produced, and the identification of each species will be possible. Flying insects have evolved to identify and communicate with each other by using their specific wingbeat frequency, and this offers a unique and promising identification tool to the already busy but often challenging field.