Use of thermal drone in detection and assessment of larval mass temperature in decomposed rabbit carcasses

Manual ground searches and cadaver dogs are traditional methods for locating remains, but they can be time- and resource-intensive, resulting in the decomposition of bodies and delay in victim identification. Therefore, thermal imaging has been proposed as a potentially useful tool for detecting remains based on their temperature. This study investigated the potential of a novel search technique of thermal drones to detect surface remains through the detection of maggot mass temperatures. Two trials were carried out at Selangor, Malaysia, each utilizing 12 healthy male Oryctolagus cuniculus European white rabbits and DJI Matrice 300 RTK drone China, equipped with a thermal camera; Zenmuse H20T to record the thermal imaging footage of the carcasses at various heights (15, 30, 60–100 m) for 14 days for each trial. Our results demonstrated that the larval masses and corresponding heat emissions were at their largest during the active decay stage; therefore, all the carcasses were observable in thermal images on day 5 and remained until day 7. Statistical analyses showed that (1) no statistically significant differences in thermal images between clothed and unclothed subjects (p > 0.05); (2) 15 m above ground level was proven to be the optimal height, as it showed the greatest contrast between the carcass heat signature and the background (p < 0.005). Our data suggested the potential window of detection of thermal signatures was detectable up to 7 days post-deposition. This could be an important guideline for the search and recovery teams for operational implementation in this tropical region.     

The Effect of Clothing on the Rate of Decomposition and Diptera Colonization on Sus scrofa Carcasses

Twenty Sus scrofa carcasses were used to study the effect the presence of clothing had on decomposition rate and colonization locations of Diptera species; 10 unclothed control carcasses were compared to 10 clothed experimental carcasses over 58 days. Data collection occurred at regular accumulated degree day intervals; the level of decomposition as Total Body Score (TBS_surf), pattern of decomposition, and Diptera present was documented. Results indicated a statistically significant difference in the rate of decomposition, (t₄₂₇ = 2.59, p = 0.010), with unclothed carcasses decomposing faster than clothed carcasses. However, the overall decomposition rates from each carcass group are too similar to separate when applying a 95% CI, which means that, although statistically significant, from a practical forensic point of view they are not sufficiently dissimilar as to warrant the application of different formulae to estimate the postmortem interval. Further results demonstrated clothing provided blow flies with additional colonization locations.     

Tracking Movement and Temperature Selection of Larvae of Two Forensically Important Blow Fly Species Within a “Maggot Mass”

The current study responds to the lack of understanding about the temperatures experienced by individual blow fly larvae within “maggot masses.” The temperature selection of both aggregating (in a mass) and nonaggregating larvae was compared and their pattern of movement assessed. Infrared imaging determined the temperatures within a mass and in the vicinity of the constituent individual larvae, whose movements were tracked by dyeing their tissues red. Individual Chrysomya rufifacies larvae selected temperatures above 27°C, significantly higher than the temperature selected by Calliphora vicina larvae (24.5°C). However, this same difference was not seen within a mass, with both species selecting temperatures around 28°C. Larval movement in a mass was nonrandom, indicating that larvae actively select their position in a mass. Furthermore, larvae have a strong tendency to select the hottest part of a mass; therefore, maximum mass temperatures might provide a reliable proxy for the actual temperatures experienced by larvae.     

An Experiment to Characterize the Decomposer Community Associated with Carcasses (Sus scrofa domesticus) on Oahu,Hawaii

Pig (Sus scrofa domesticus) carcasses were decomposed on the soil surface of a terrestrial habitat on the island of Oahu, Hawaii to begin characterizing the decomposer community. Results showed that carcasses can decompose rapidly on Oahu, primarily due to the activity of fly larvae, with ~80% of mass lost by 8 days (~220 ADD) postmortem. Scavenging was conducted exclusively by the small Indian mongoose (Herpestes javanicus), first feeding on larvae then feeding on the remains. Carcasses were habitats of warm temperature, little to no oxygen, slightly acidic/neutral pH, and high sodium concentration. Larval masses selected for a microbial community comprised of multiple bacterial taxa from phyla Firmicutes and Proteobacteria, particularly genera Clostridium, Proteus, and Providencia. These larval masses were well established from 3 to 8 days (~90 to ~220 ADD) postmortem. These data provide helpful, novel insight into the structure and activity of carcass decomposer communities on Oahu.     

Decomposition and insect succession of clothed and unclothed carcasses in Western Australia

The effect of clothing on carcass decomposition and patterns of insect succession onto remains were investigated in two separate years during autumn in Western Australia. The progression of decomposition differed between clothed and unclothed carcasses in both years of the study. The presence of clothing markedly prolonged the wet decay stage in both years with larval feeding occurring across the moist skin surface underneath clothing, as well as within and under the carcasses. Ambient temperatures were higher in the second year of the study and corresponded to marginally faster rates of decay throughout decomposition. Within years, insect arrival and oviposition were largely consistent between clothed and unclothed carcasses with a few notable exceptions. The green blow fly, Lucilia sericata Meigen (Diptera: Calliphoridae) oviposited one day earlier on clothed than unclothed carcasses in both years of the study. The black carrion fly, Australophyra rostrata Robineau-Desvoidy, (Diptera: Muscidae) colonised clothed carcasses in two distinct waves of succession but only one wave of ovipoistion was observed on unclothed carcasses in either year. Correspondingly, clothed carcasses supported larval feeding by A. rostrata for a longer duration than unclothed carcasses. Finally, dipteran larval masses were more widely distributed across the carcass surface and were present for a longer period of time on clothed carcasses than on unclothed carcasses in both years. Forensically relevant data detailing the seasonal pattern of insect succession onto clothed and unclothed decomposing remains in Western Australia are reported.     

Determination of Calliphoridae (Diptera) Fauna and Seasonal Distribution on Carrion in Ankara Province*

Abstract: This study was conducted from March 2006 to 2007. The aim of the study was to determine the forensically significant Calliphoridae (Diptera) species and their seasonal distribution in Ankara province at Beytepe Campus. Pig carcasses were killed by a veterinary using pentobarbital sodium with intervals from 2 to 3 weeks to a month. Samples were collected from the carcass everyday in the morning, in the afternoon, and at sunset. Temperature and parameters of weather, such as cloudy, sunny, rainy, and snowy, were recorded at each visit. Phaenicia sericata (Meigen), Chrysomya albiceps (Wiedemann), Calliphora vomitoria (Linnaeus), and Calliphora vicina (Robineau‐Desvoidy) species, which belong to Calliphoridae family, were collected. It was shown that the seasonal distribution of the collected species was different from each other. The species were determined on carcass between the following times; P. sericata, from April to November; C. albiceps, from May to November; Ca. vomitoria, from February to June and from September to December; and Ca. vicina, from February to May and in June and September. Calliphoridae fauna and its annual seasonal distribution in Turkey on 12 pig carcasses were reported for the first time in this study.     

A Preliminary Study of Insect Succession in Al‐Ahsaa Oasis,in the Eastern Region of the Kingdom of Saudi Arabia

Rabbit carcass decomposition was examined in four seasons in Al‐Ahsaa Oasis. Decomposition rate was significantly faster in summer compared with other seasons. Fourteen insect species from four orders and seven families were recorded: Calliphoridae, Muscidae, Sarcophagidae, Formicidae, Histeridae, Dermestidae, and Tenebrionidae. Most of the fly maggots collected were Calliphoridae with only one species from both Muscidae and Sarcophagidae. Maggots of Calliphora vicina (R.‐D.) and Chrysomya albiceps (Wiedemann) colonized the carcasses in all seasons while both Ch. bezziana (Villeneuve) and Lucilia sericata (Meigen) were found in all seasons except for winter. Maggots of Chrysomya megacephala (F.) and Phormia regina (Meigen) were only collected in the summer and autumn, respectively. Four coleopteran species were collected: Hymenorus sp., Saprinus chacites (Illiger), Dermestes maculatus DeGeer and Blaps sp. One formicidian species, Pheidole megacephala (F.), was observed in all seasons. Insect richness was greater, and decomposition rate was faster in summer compared with other seasons.     

Postfeeding Larval Dispersal Behavior of Late Season Blow Flies (Calliphoridae) in Southern Ontario,Canada

Postfeeding dispersal involves migration of larvae away from their food source in order to pupate. Puparia are difficult to find, yet are important for estimating PMI, and missing puparia during collection can result in inaccurate estimations. This study investigates the late season maggot dispersal patterns for blow flies at coyote carcasses in two habitats with an aim to improving puparia collection procedures. Puparia samples collected from various dispersal distances and directions tested the spatial distribution patterns of the various species using the variance/mean ratio (VMR). Lucilia illustris was the most common species to emerge, with a preferred minimum dispersal distance of more than 50.8 cm and an overall VMR value of 14.91, indicating this species had a clumped distribution pattern. These findings highlight that current collection procedures that use random sampling from under carcasses do not adequately account for the spatial distribution of larvae.     

Carrion fly (Diptera: Calliphoridae) larval colonization of sunlit and shaded pig carcasses in West Virginia, USA

Two pig (Sus scrofta L.) carcasses were placed in sunlit and shaded plots in September 2003, and again in May 2004. Mean ambient temperatures between sunlit and shaded plots were not significantly different in either September or May, but mean ambient temperatures at sunlit and shaded plots in 2004 were significantly higher than corresponding means for sunlit and shaded plots in 2003. Mean maggot mass temperatures were significantly higher than ambient plot temperatures for all four experimental plots (i.e., sunlit and shaded carcasses in both 2003 and 2004). In addition, maggot mass temperatures on sunlit carcasses were positively, and significantly, correlated with ambient temperatures, whereas there was no significant correlation between maggot mass and ambient temperatures at shaded plots. Carcass decomposition proceeded more rapidly in 2004 in the presence of higher ambient temperatures, and sunlit carcasses decomposed faster than shaded ones in both 2003 and 2004 experiments. Phaenecia coeruleiviridis (Macquart) and Phormia regina (Meigen) third instars dominated collections on all four carcasses, but there was little temporal overlap between these species with third instars of the former dominating collections in the early portion (approximately 40%) of each experimental period (with the exception of the shaded carcass in 2004 where both species were co-dominant), and the latter assuming dominance in the latter portion (approximately 60%). Lower accumulated degree hour values were calculated for instar development on 2004 carcasses subjected to higher ambient temperatures.     

The succession and development of insects on pig carcasses and their significances in estimating PMI in south China

The succession of insect communities on carrion varies at local and global spatial scales. As such, ecological succession data obtained from corpses at one geographic location cannot necessarily be applied to other locations. Our study describes this succession in the far southern part of China to provide such data for forensic cases in this region. A total of 18 pig carcasses were placed in the field in four seasons, and the timing of the following events were recorded: appearance of larvae, onset of larval wandering, when most larvae had wandered, onset of pupariation, when most larvae had pupariated, onset of eclosion and end of eclosion. Our results indicated that all of the evaluated events could be used as accurate indicators of postmortem interval (PMI). The carcasses decayed fairly quickly in spring, summer and autumn, taking 225+/-75 h, 183+/-44 h, and 247+/-70 h, respectively, to decay from the fresh stage to skeletonisation. In winter, carcasses needed longer (1180+/-291) to decay as much. Carcasses attracted 47 species of insect, with flies predominating. The larvae were mainly Chrysomya megacephala (Fabricius), Chrysomya rufifacies (Macquart) and Hydrotaea (Ophyra) spinigera (Stein). Most necrophagous insects were found all year around, and there were no marked differences in species among the four seasons, except that Dermestes maculatus (De Geer) was absent in winter. Blowflies produced only one generation on a carcass before it became skeletonised, which simplified the estimation of PMIs.     

Comparison of Decomposition Rates and Faunal Colonization of Carrion in Indoor and Outdoor Environments

Abstract: Decomposition and insect colonization of pig (Sus scrofa L.) carcasses were observed over a 42‐day period inside and outside a house in a suburban region of Edmonton, Alberta. Three freshly killed pig carcasses were placed outdoors on grass and three carcasses were placed in separate rooms inside a house in a suburban residential area. The carcasses were examined and sampled regularly. Outside carcasses were colonized rapidly by Calliphora vicina (R‐D), Lucilia sericata (Meigen), Lucilia illustris (Meigen), Eucalliphora latifrons (Hough), Cynomya cadaverina (R‐D), Phormia regina (Meigen), and Protophormia terraenovae (R‐D). There was a delay of 5 days before inside carcasses were first colonized but all species except E. latifrons and L. illustris readily colonized at this time. Many more insects colonized the outside carcasses, and these were rapidly skeletonized. Inside, much fewer insects were present and decomposition was slowed and colonization extended. Dispersal patterns of postfeeding larvae inside the house on hard substrate were greatly expanded compared with those from carcasses on grass.     

Forces Required for a Knife to Penetrate a Variety of Clothing Types

In stabbing incidents, it is usual for the victim to be clothed and therefore a knife penetrates both clothes and skin. Clothes (other than leather) have been thought to make little difference to the penetration force. However, there is little quantitative data in the literature. In this study, a range of clothes have been tested, either singly or in layers of, for example, T‐shirt and shirt, to quantify the additional force required when clothes are present. A materials testing system has been used to test the penetration force required to stab through clothes into a foam–silicone rubber skin simulant. The results show that the force required can be significantly different, particularly when layers of clothing are penetrated. A cotton t‐shirt adds c. 8 N to the penetration force, while a T‐shirt and jacket can add an additional 21 N. The results allow a more quantitative assessment of forces required in stabbing.     

A Preliminary Examination of Differential Decomposition Patterns in Mass Graves

Five pairs of mass graves, each containing carcasses of 21 rabbits, were used to examine differential decomposition at four locations within the burial: surface, deep, mid‐outer, and core. Every 100 accumulated degree days (ADD), a pair of graves was exhumed, and total body score (TBS) and internal carcass temperature of each rabbit were recorded. Decomposition did not differ for core‐ and deep‐positioned carcasses (p = 0.13); differences were significant (p < 0.001) for all other location comparisons. Decomposition occurred fastest in shallow carcasses, followed by mid‐outer carcasses; deep and core carcasses decomposed slowest and at rates not significantly different from one another. Adipocere formation was minimal and confined to deep carcasses. Carcass location within the mass grave significantly influenced internal carcass temperature (p < 0.001); a mean internal temperature difference of ca. 1°C existed between deep and shallow carcasses (30 cm apart). Effects of mass compactness and oxygenation require further investigation.     

Application of forward‐looking infrared (FLIR) imaging from an unmanned aerial platform in the search for decomposing remains

Traditional methods of cadaver detection in outdoor environments include manual ground search, cadaver dogs, and manned aerial reconnaissance during daylight. These methods have limitations; however, a potential low‐cost alternative may be to employ thermal imaging equipment mounted on an unmanned aerial vehicle (UAV) to detect heat emitted by insect and bacterial activity on the decomposing remains. No studies have addressed the influence of wrappings on detection of maggot mass thermal signatures nor assessed thermal detection of smaller body fragments. We addressed these knowledge gaps by utilizing a two‐phase experimental approach to explore thermal detection of carcasses using UAV‐mounted infrared imaging. In Phase 1, pig body fragments were deposited on the surface or shallow buried. In Phase 2, whole pig carcasses were deposited in four conditions: on the surface uncovered, wrapped in plastic or carpet, or buried. Our results demonstrated that observable heat emissions from remains corresponded to peak insect activity during active decay and could be readily detected in uncovered whole carcasses and fragments. Although plastic and carpet wrappings partly impeded detection of insect heat signatures, these materials were clearly detectable themselves because of their contrast to the background ground surface. Thermal signatures of buried partial remains and disturbed gravesoil were also observed; however, the buried whole carcass transitioned to adipocere prior to the decay stage and without any insect colonization or heat signature. These data can inform operational implementation of this technique to complement existing search strategies to offer a robust, low‐cost alternative for use where scene characteristics allow.     

Impact of plastic wrapping on carcass decomposition and arthropod colonisation in northern Africa during spring

The effect of plastic wrapping on decomposition rate and carrion fauna of rabbits (Oryctolagus cuniculus L.) was examined in spring in a semi-urban area in North Algeria. All decomposition stages were observed in all carcasses, with the same durations in the control but different durations in the wrapped carcasses. Decomposition of the carcasses in the plastic wrapping was significantly slower than that of the exposed ones. A total of 12,516 specimens, belonging to 36 families and 69 species, were morphologically identified. Thirteen species of forensic relevance were also identified at the molecular level using the cytochrome c oxidase I (COI) barcode region, and the sequences were submitted to online databases. Wrapping had a significant effect on species composition (χ² = 569.269, df = 55, p < 0.001). Higher species richness, abundance, and diversity were found in the control group. No significant difference in species abundance was observed between the treatments. The plastic wrap did not influence the accessibility of carcasses to insects, nor did it delay the arrival of necrophagous flies. This study provides basic information on the decomposition and arthropod colonisation of wrapped remains and contributes to the literature on North African carrion fauna.     

Influence of rain and malathion on the oviposition and development of blowflies (Diptera: Calliphoridae) infesting rabbit carcasses in Kelantan, Malaysia

The influence of rain and malathion on the initial oviposition as well as development of blowfly species infesting rabbit carcasses decomposing in sunlit and shaded habitats were studied over a period of 1 year in Kelantan, Malaysia. Chrysomya megacephala (Fabricius) was the most dominant species that infested the carcasses, followed by Chrysomya rufifacies (Macquart). In general, rain, depending on its intensity, delayed initial oviposition by 1–2 days and prolonged the pupation period by 1–3 days. The presence of malathion in the carcasses delayed initial oviposition by 1–3 days and prolonged the pupation period by 2–3 days. These findings deserve consideration while estimating postmortem interval since rain is a commonplace occurrence in Malaysia and malathion is one of the common poisons as an agent for choice to commit suicide.     

Analysis of the Effect of Cyclophosphamide and Methotrexate on Chrysomya megacephala (Diptera: Calliphoridae),

Forensic entomotoxicology investigates the effects of chemical substances in the development of scavenger insects and the reflection on estimating the minimum postmortem interval (PMI). To evaluate the impact of the chemotherapeutic drugs cyclophosphamide (CF) and methotrexate (MTX) on the postembryonic development of Chrysomya megacephala, controlled experiments were performed by rearing the larvae on spiked minced beef with different concentrations of these drugs. The results indicated that CF significantly decreased their developmental rate up to 28 h but had no significant effect on larval and adult sizes, survival rate, and sex ratio, whereas MTX decreased larval and adult sizes, survival rate, and there was a deviation in the expected sex ratio toward females in MTX‐exposed larvae but had no significant impact on developmental rate. These negative interference factors should be considered in cases of suspected death of people that have undergone chemotherapy.     

Spread and habitat selection of Chrysomya albiceps (Wiedemann) (Diptera Calliphoridae) in Northern Italy: forensic implications

Abstract: Habitat selection exploited by Chrysomya albiceps during its initial spread in Northern Italy was analyzed in relation to landscape structure. The results of two short studies and a case report are here discussed. C. albiceps was not found on experimental pig carcasses in the urban area of Pavia. It was missing in the woody mountains surrounding Lecco, but it was found in the same area, at a lower altitude, within the typical “urban sprawl” landscape. It was then recorded in a natural reserve, among a rich carrion‐fly population. Indications coming from habitat selection suggest that C. albiceps has not yet saturated its potential ecological niche in newly colonized areas of Northern Italy. Factors like temperature, altitude, and interspecific competition can act as limiting factors, affecting habitat selection and distribution in newly colonized areas; the influence of those factors has to be taken into account for forensic purposes.     

Fluorescence Imaging of Posterior Spiracles from Second and Third Instars of Forensically Important Chrysomya rufifacies (Diptera: Calliphoridae),

Entomological protocols for aging blowfly (Diptera: Calliphoridae) larvae to estimate the time of colonization (TOC) are commonly used to assist in death investigations. While the methodologies for analyzing fly larvae differ, most rely on light microscopy, genetic analysis, or, more rarely, electron microscopy. This pilot study sought to improve resolution of larval stage in the forensically important blowfly Chrysomya rufifacies using high‐content fluorescence microscopy and biochemical measures of developmental marker proteins. We established fixation and mounting protocols, defined a set of measurable morphometric criteria and captured developmental transitions of 2nd instar to 3rd instar using both fluorescence microscopy and anti‐ecdysone receptor Western blot analysis. The data show that these instars can be distinguished on the basis of robust, nonbleaching, autofluorescence of larval posterior spiracles. High‐content imaging techniques using confocal microscopy, combined with morphometric and biochemical techniques, may therefore aid forensic entomologists in estimating TOC.     

A Checklist of Calliphoridae Blowflies (Insecta,Diptera) Associated with a Pig Carrion in Central Brazil*

Abstract: Although the Cerrado is the second major Brazilian biome, few studies have been undertaken about its entomofauna. Blowflies have an important role in forensic entomology, helping in the determination of postmortem intervals. The main goal of this exploratory study was to identify and to catalog the blowfly species associated with a pig carcass. The study was conducted in a pasture in Brasília, Distrito Federal. A pig (Sus scrofa) was killed with a .22 caliber shot in the frontal region of the head. Adult blowflies were surveyed daily from June 1 through 30, 2004. A total of 14,910 adult calliphorids were collected, representing eight species: Chrysomya albiceps, C. megacephala, Cochliomyia macellaria, Chloroprocta idioidea, Hemilucilia semidiaphana, H. segmentaria, Lucilia cuprina, and L. eximia. C. albiceps was the most frequent species, amounting to 94.76% of the catch. Five decomposition stages were observed, and for calliphorids, the most attractive stage was the bloated one.