Forensic entomotoxicology revisited-towards professional standardisation of study designs

Development of mixed linear models to analyze and describe the impact of malathion on the larval growth of Megaselia scalaris (Diptera: Phoridae) under various feeding media and environmental conditions

Forensic entomology plays a crucial role in estimating the minimum postmortem interval through the study of insect larvae found at crime scenes. The precision of this estimation relies on various biotic and abiotic elements that simultaneously influence insect growth and development, encompassing factors such as temperature, humidity, photoperiod, diet, and the existence of xenobiotics in decomposing tissues. Despite numerous studies on the influence of these factors, including the impact of xenobiotics, there are currently no robust tools available for making corrections to this estimation considering concurrently all variables. In an attempt to propose an exploratory and descriptive statistical model to analyze the simultaneous effect and interaction of different variables on larval growth, this study aimed to compare the effect of malathion on the growth of Megaselia scalaris (Loew, 1866) (Diptera: Phoridae) raised in malathion-spiked porcine muscle, under controlled and uncontrolled temperature and humidity conditions (environmental conditions). Larvae were also reared using various growth media. A split-plot design that combined crossed and nested factors was employed; 2 linear mixed models were developed to assess the relationships between the variables. The model provides valuable insights into the complex interactions among xenobiotics, growth media, and environmental conditions in the size and development of M. scalaris.

Comparative Toxicological Analyses of Traditional Matrices and Blow Fly Larvae in Four Cases of Highly Decomposed Human Cadavers

In forensic investigation, determining the time and cause of death becomes challenging, especially in cases where the remains are found in advanced decomposition, rendering traditional toxicological samples unavailable or unreliable. Entomotoxicology, an emerging methodology within forensic science, leverages insect specimens collected from cadavers as alternative toxicological samples. Several laboratory and field research studies have highlighted the efficacy in detecting various drugs, toxins, and elements absorbed by insects feeding on cadaveric tissues, even at low concentrations. However, correlation studies between drug concentrations in conventional matrices and insects remain controversial due to unknown factors influencing drug metabolism and larval feeding activity. This paper presents four real cases in which human cadavers were discovered in advanced stages of decomposition, and toxicological analyses were performed on both insect samples and available matrices. The results presented complement the scant literature currently available on the application of entomotoxicology in real cases, providing insights into the correlation between larvae and human specimen results. Furthermore, guidelines to collect and preserve entomological evidence at the crime scene and during the autopsy for use in entomotoxicological analyses are provided. This advancement holds promise in aiding forensic investigations, particularly in cases where traditional methods cannot be applied or require supporting data for further validation.

From Deutsche Zeitschrift to International journal of legal medicine-100 years of legal medicine through the lens of journal articles, Part 4: International journal of legal medicine from 1990 to 2022

This is the fourth and final paper in a series related to the analysis of articles published in this journal during its first 100 years of activity. This article covers the time span from 1990 to 2022. It is important to note that, given the period covered by this analysis, it does not aim to provide a historical overview but rather an examination of the most recent trends in our discipline compared to the past. Between 1990 (Volume 104) and 2022 (Volume 136), 4004 articles were published in the International Journal of Legal Medicine (IJLM) across 33 volumes. This corresponds to 53% of all the articles published since the launch of the journal. When compared to the period from 1970 to 1990, some categories no longer appear to be as relevant (e.g., sexual medicine, 1 article; social medicine, 0 articles; biography, 3 articles; history, 4 articles). Conversely, the most recent period has shown an increasing importance in forensic genetics (1388 articles) and the emergence of new significant topics that merit their own classification, such as age estimation (286 articles), forensic anthropology (189 articles), forensic imaging (150 articles), and forensic entomology (90 articles).

Forensic analysis of mosquito blood meal digestion process and the impact of heroin opiate: determination of the post-feeding interval as a PMI estimation

Females of some mosquito species are anthropophilic, as they feed on human blood to support egg production and, hence, are forensically valuable if found at a crime scene. The present study investigated the blood meal digestion process in Culex pipiens L. both with and without heroin and proposed a method for estimating the post-feeding interval (PFI). Mosquitoes were fed on a control mouse, a heroin-injected mouse, or in vitro heroin-treated mouse blood. The blood meal digestion was then investigated at different hours post-feeding. Data showed that the blood meal size ingested by control mosquitoes was 0.681 ± 0.04 mg/mosquito and was completely digested within 45 h post-feeding. An estimation of the PFI was proposed in terms of the rate of hemoglobin (Hb) digestion. The blood meal size of the mosquitoes fed on the in vitro heroin-treated blood and the heroin-injected mouse was 0.96 ± 0.06 and 0.79 ± 0.01 mg/mosquito and was completely digested within 50 and 55 h post-feeding, respectively. The digestion of Hb started similarly in all experimental mosquitoes until 10 h post-feeding, after which it significantly decreased in heroin-treated blood meals compared with the control ones. This may suggest that heroin impacted the digestion process, as it took an extra 5-10 h to complete. These findings could be valuable in the forensic context since an estimation of PFI is proposed as a potential estimation of the postmortem interval (PMI). However, care should be taken as heroin in the host blood has significantly impacted the overall digestion process and, hence, may bias the PFI/PMI estimation.

Effects of aluminium phosphide on larval morphometry of two important Chrysomya species

Chrysomya megacephala and C. rufifacies are globally predominant species of blowflies that are amongst the primary colonisers of decomposing carcasses. The development of blowflies has been studied extensively to estimate the minimum postmortem interval (PMImin). This article evaluates the effect of aluminium phosphide (AlP) on the larval morphometry and life cycles of C. megacephala and C. rufifacies. The rabbits were given different dosages of AlP and their livers were excised to rear C. megacephala and C. rufifacies. Through multiple-regression analysis, we assessed the overall impact of varying dosages of AlP on larvae of both species. AlP accelerated development until pupation, whilst the time until emergence remained the same. At higher concentrations, AlP had a positive effect on the development of these species. Since both species are abundant, forensic entomology studies examining the effect of AlP on morphometry and developmental stages would provide valuable information to investigators assessing PMImin.

Effects of Terbufos (Organophosphate) on Larval Behaviour of Two Forensically Important Diptera Species: Contributions for Entomotoxicology

Neurotoxicant compounds interfere with the behaviour and biology of insects, significantly altering their locomotion patterns. However, little is known about the effect of organophosphates, neurotoxicants for agricultural, domestic and industrial use, on the larval movement of necrophagous flies, although being responsible for frequent cases of poisoning and accidental or intentional deaths. Thus, we aimed to study the influence of Terbufos (organophosphate) on the activity and mobility patterns of Lucilia eximia (Wiedemann 1819) (Calliphoridae) and Peckia (Peckia) chrysostoma (Wiedemann 1830) (Sarcophagidae) immatures collected from rat carcasses intoxicated with 5, 10 or 20 mg/kg of Terbufos, to evaluate (i) peristaltic movements and body contractions, and (ii) distance and shape of the trajectory travelled by the larva. Behavioural parameters were analysed in loco and through videos. We observed that the presence of Terbufos altered poisoned larvae's activity and body mobility in both taxon and dose-dependent manner. Lucilia eximia larvae were more active, with greater frequency of body movements and lateral contractions when intoxicated with high and intermediate doses of Terbufos. On the other hand, P. (P.) chrysostoma immatures were less active, with fewer body and lateral contractions when intoxicated with the high dose of the compound. This work experimentally demonstrates that the presence of Terbufos can alters the mobility and movement of intoxicated necrophagous Diptera, essential components of the cadaveric fauna.

In the case of extensively putrefied bodies, the analysis of entomological samples may support and complement the toxicological results obtained with other alternative matrices

Entomotoxicological analysis is not part of routine toxicological analysis. This work aims to present two cases to illustrate the potential of entomological samples as complementary matrices to identify substances in cases of advanced putrefaction. (Case#1) A woman wasexhumed after 14 months to ascertain the exact cause of death. She died after six weeks of hospitalization because of intestinal ischemia followed by multiorgan failure. (Case#2) The corpse of a woman, known to have a psychiatric disorder, was discovered in her apartment. The state of decomposition of the body was consistent with a post-mortem period of several weeks (approximately 6 weeks). Toxicological investigations were performed in the biological and entomological samples of case#1 (hair, adipocere, brain, and pupae) and of case#2 (hair, bone, flies, and pupae) using liquid chromatography with high-resolution mass spectrometry and tandem mass spectrometry detection methods. In case#1, several drugs and metabolites were detected. In particular, the pupae analyses allowed the objectification of morphine administration, whereas morphine was only found in adipocere, but not in hair nor in brain. In case#2, the pupae analyses allowed the detection of three metabolites of quetiapine, and the flies analyses allowed the detection of valpromide, which was only detected in hair. In conclusion, the pupae and flies analyses in these two cases complemented the results obtained in the other alternative biological samples, which may guide hypotheses about the possible causes of death. Nevertheless, additional data and case reports would be of benefit to assess the value of entomotoxicology in routine forensic investigations.

The Effect of Different Heavy Metals on the Development of Lucilia sericata (Diptera: Calliphoridae)

This study investigates the impacts of three different heavy metals at different concentrations on some life-history traits of Lucilia sericata (Meigen 1826) (Diptera: Calliphoridae). First-instar larvae of L. sericata were reared on a diet containing four concentrations (0.25, 0.50, 1, and 2 µg/g) of the heavy metals (cadmium, zinc copper). The parameters measured were larval and pupal mortality, larval length, adult, pupal, and larval weight, and development time. Larval and pupal survival decreased as heavy metal concentrations increased. Pupal weight was significantly different among heavy metals andc oncentrations, but the adult weight was not significantly different among heavy metals and concentrations. The larval length was significantly different among concentrations and heavy metals. This study reveals that the presence of heavy metal in carrion or the carrion environment should be inconsidered when estimating the time of colonization in forensic investigations.

Unexpected results found in larvae samples from two postmortem forensic cases

Purpose

In forensics, entomological specimens can be used as additional/alternative matrices to detect xenobiotics when human specimens are limited in their application. Despite some advantages over implementing putrefied human remains, most medico-legal laboratories do not include entomotoxicological procedures as routine analytical methods. We thus applied two authentic cases to evaluate necrophagous larvae’s potential as complementary matrices for toxicological analysis after extensive postmortem decomposition.

Methods

Larvae and postmortem human samples, including hair, stomach contents, pericardial fluid, liver, lung, and skeletal muscle, were collected at autopsy. Samples were analyzed by liquid chromatography–tandem mass spectrometry and liquid chromatography–quadrupole time-of-flight mass spectrometry for pharmaceutical substances, illicit drugs, and new psychoactive substances, including synthetic cannabinoids, benzodiazepines, new synthetic opioids, and stimulants.

Results

Nearly all substances detected in human specimens, including several benzodiazepines and synthetic cannabinoids, were also detected in larvae. Surprisingly, some drugs, including the new psychoactive substances EAM-2201 and U-47700, were found exclusively in larvae and hair. The benzodiazepine etizolam was detected only in liver, lungs, and stomach contents, possibly resulting from characteristic tissue distribution in humans and/or larvae.

Conclusions

Antemortem external hair contamination with synthetic cannabinoids from side-stream smoke and postmortem hair contamination with substances in putrefaction fluids can be supposed in these cases. Our findings suggest that supplementary information can indeed be gained from analyzing larvae additional to those human specimens that are typically used for toxicological analysis after extensive postmortem decomposition. Nevertheless, these results represent merely two cases, requiring in-depth studies to determine whether such findings can identify acute intoxications as possible causes of death.

Seasonal Impact of Heroin on Rabbit Carcass Decomposition and Insect Succession

This study investigates the succession of insects and the length of the decomposition of rabbit carcasses injected with heroin. In total, 24 rabbits (2-2.5 kg, Oryctolagus cuniculus domesticus L.) were used in the study. Twelve carcasses were exposed to insect activity in winter (January and February) and 12 in summer (July and August) in Riyadh, Saudi Arabia. Three replicate experiments were conducted in each season. For each experiment, three rabbits were injected with varying doses of heroin, and the fourth rabbit was used as a control, being injected only with saline solution. Insects belonging to the order Diptera, Coleoptera, and Hymenoptera were attracted to the carcasses. In both of the investigated seasons, heroin appeared to delay the decomposition process but did not have a significant impact on the number of insects. In general, the number of flies in both seasons was substantially higher than that of beetles and ants. During the summer, flies were more attracted to treated carcasses with a higher dose of heroin. Some flies such as Musca domestica L. (Diptera: Muscidae) and Chrysomya albiceps Wiedemann (Diptera: Calliphoridae) and some beetles such as Pimelia boyeri Solier (Coleoptera: Tenebrionidae) were represented on the carcasses by different developmental instars (larvae, pupae, and adults). Overall, heroin has not potential effects on the insect succession patterns of insect, however, influences the decomposition of rabbit carcasses. These findings are important while using insects in medicolegal investigation, since heroin is one of the common poisons used as an addictive agent.

Forensic Entomology in China and Its Challenges

Simple Summary

Forensic entomologists utilize sarcosaprophagous insect species to estimate the postmortem interval to aid death investigations. In this paper, we present the recent chronology of forensic entomology in China and illustrate how identification, development, and succession data are obtained and applied at the scale of such a large country. To overcome the difficulties and challenges forensic entomology faces in China, a number of countermeasures are provided.

Abstract

While the earliest record of forensic entomology originated in China, related research did not start in China until the 1990s. In this paper, we review the recent research progress on the species identification, temperature-dependent development, faunal succession, and entomological toxicology of sarcosaprophagous insects as well as common applications of forensic entomology in China. Furthermore, the difficulties and challenges forensic entomologists face in China are analyzed and possible countermeasures are presented.

Lead toxicity in Lucilia cuprina and electrochemical analysis: a simple and low-cost alternative for forensic investigation

Entomotoxicology allows the detection and analysis of substances such as poisons, drugs, and metals in necrophagous insects using analytical protocols. In a forensic situation related to death by gunshot, the gunshot residue (GSR) is dispersed at the crime scene and may be consumed by necrophagous insects. Lead (Pb) is the most abundant metal in GSR samples and it can be determined using non-portable methods. However, the toxicity effects of GSR samples on Lucilia cuprina (Diptera: Calliphoridae) and the detection of Pb via portable electrochemical methods have not been investigated. This study describes for the first time the toxicity analysis of Pb on immature L. cuprina through their survival rate and influence of Pb on immature development. In addition, the bioaccumulation of Pb in the larvae samples was determined based on square wave anodic stripping voltammetry (SWASV) measurements. The results revealed a low limit of detection to Pb (6.5 μg L^-1) and the analytical performance was satisfactory because it measures Pb levels in larvae exposed to a diet containing 50 μg Pb g^-1. Furthermore, the levels of Pb influenced the survival rate and development time of the immature L. cuprina. Larvae exposed to a high concentration of the metal (50 μg Pb g ^-1) showed statistically significant changes (p < 0.05). The presence of Pb in immature L. cuprina can be used to estimate the post-mortem interval; thus, the present study provides important information in forensic entomology.

Puparial Cases as Toxicological Indicators: Bioaccumulation of Cadmium and Thallium in the Forensically Important Blowfly Lucilia sericata

In this study, we present entomotoxicological data on the accumulation of cadmium and thallium in a forensically important blowfly, Lucilia sericata, and evaluate the reliability and utility of such information as toxicological evidence for poisoning as a cause of death. We observed that Cd and Tl content in different growing stages of L. sericata (larvae, puparial cases, and adults) was increasing with increasing metal concentration in the feeding substrate, namely metal-enriched liver. However, patterns of accumulation differed between the two metals investigated, showing a linear relationship for Cd and a saturable pattern for Tl. For cadmium, the highest bioaccumulation factor (BAF) was found in the larval stage (in the range of 0.20–0.25), while for thallium, puparial cases accumulated more metal than the other stages tested (BAF in the range of 0.24–0.42). Thallium was also observed to have a negative effect on larval growth, resulting in lower weight and smaller puparial size. With this study, we update the information on the bioaccumulation of cadmium in forensically important blowflies and provide the first report on the bioaccumulation of thallium as well as its developmental impact in blowflies. Specifically, our results suggest that analysis of puparial cases could yield useful information for entomotoxicological investigations. The content of Cd and Tl in larvae, puparial cases, and adults of L. sericata was determined by inductively coupled plasma mass spectrometry (ICP-MS). The validation parameters of the method such as sensitivity, detection limits, quantification limits, precision, and accuracy were evaluated. The method detection limit (MDL) for all types of samples was in the range of 1.6–3.4 ng g⁻¹ for Cd and 0.034–0.15 ng g⁻¹ for Tl, and the accuracy of the method was confirmed by a high recovery of metals from certified reference materials (91.3% for Cd and 94.3% for Tl).

The implication of morphometrics and growth rate of dipteran flies in forensic entomotoxicology research: a review

Forensic entomotoxicology integrates toxicology into forensic entomology to estimate minimum postmortem interval (PMI_min) and circumstances of death where toxicants and poisonous substances are the suspected cause of death. Forensic entomotoxicology not only confirms the presence of toxicants in insects feeding off a cadaver but also studies its effect on the bio-morphometry and growth rate of insects. This review article highlights the effects of various toxicants on forensically important species of dipteran flies. It also discusses the parameters that may affect accuracy in estimation of time since death. The bio-physical effects of toxicants (excluding the analytical approach for qualitative detection) would help understand the trends in forensic entomotoxicological research worldwide.

Revisiting the concept of entomotoxicology

Until now, the term entomotoxicology has only been used in medico-legal sciences. However, entomotoxicology as a whole has a much wider scope and forensic entomotoxicology is just one of its branches. Based on the literature a wider definition of the term is presented. Today, we can distinguish two major branches of entomotoxicology: 1) Forensic entomotoxicology, which uses the insects as evidence of the presence of xenobiotics in decomposing tissue during an investigation and 2) Environmental entomotoxicology, which uses the insects as bioindicators of environmental pollution in non-criminal circumstances. While forensic entomotoxicology is a relatively new discipline, research in environmental entomotoxicology began as far back as the 1920s. A review of the work in entomotoxicology from the last 6 years is presented, covering several interesting new trends. This article aims to redefine entomotoxicology, which should increase awareness to bring more collaborations and multidisciplinary between related scientific fields.

Effects of Methamphetamine on the Development and Its Determination in Aldrichina grahami (Diptera: Calliphoridae)

Age determination of necrophagous flies serves as an important tool for postmortem interval (PMI) estimation in forensic investigations. Drugs or toxins in cadavers may alter the developmental time of larvae, and lead to deviation in PMI estimation. Methamphetamine (MA), as one of the most abused psychostimulant drugs in Asia and North America, is often involved in forensic entomotoxicological cases. This study investigated the effects of MA (0, 45, 90, and 180 ng/mg) on the developmental rate, morphology, and survival of Aldrichina grahami (Aldrich, 1930). The results showed that 1) the developmental time to reach the pupal instar was statistically slower for the larvae reared on rabbit mince containing MA than for the control; 2) the mean length of the larvae exposed to MA concentrations was longer than those of the control; 3) the mean weight of the pupae exposed to the highest concentration of MA was significantly lighter than those of the control; 4) the GC-MS method can detect the content of MA in A. grahami immatures and empty puparia (EP).

Application of a chemiluminescence immunoassay system and GC/MS for toxicological investigations on skeletonized human remains

Hair, larvae and cardiac muscle, the only biological samples present on a skeletonized human body found in a rural area, were used for forensic toxicological analyses in order to determine possible causes of death. Since no information about the victim or the circumstances of death was available (except for the place where the corpse was found, known to be a gathering place for drug addicts), the first approach for the analysis of non-conventional matrices involved the screening of different classes of active principles, using a chemiluminescence-based screening assay designed for whole blood. The immunoassay test results showed positivity to amphetamines, cocaine and opiates on water/methanol extract from cardiac tissue, larvae and hair samples. Gas chromatography-mass spectrometry (GC/MS) analyses confirmed the immunoassay results, except for amphetamines. The minimal sample preparation (hydration and extraction in an ultrasonic bath), the reduced sample volume required for the analyses, together with the correctness of results as confirmed by GC/MS, showed the suitability of the screening test for forensic applications on non-conventional matrices. Quantitative analyses in GC/MS allowed the cause of death to be ascertained on the basis of the ratio between parent drugs and metabolites.

The uses of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) in forensic entomology

Chrysomya megacephala (Fabricius, 1794) occurs on every continent and is closely associated with carrion and decaying material in human environments. Its abilities to find dead bodies and carry pathogens give it a prominence in human affairs that may involve prosecution or litigation, and therefore forensic entomologists. The identification, geographical distribution and biology of the species are reviewed to provide a background for approaches that four branches of forensic entomology (urban, stored-product, medico-criminal and environmental) might take to investigations involving this fly.

The effect of antifreeze (ethylene glycol) on the survival and the life cycle of two species of necrophagous blowflies (Diptera: Calliphoridae)

Entomotoxicology involves the analysis of the presence and the effects of toxicological substances in necrophagous insects. Results obtained by entomotoxicological studies may assist in the investigation of both the causes and the time of death of humans and animals. Ethylene glycol (EG) is easy to purchase, sweet and extremely toxic. It may be consumed accidentally or purposefully, in an attempt to cause death for suicidal or homicidal intent. Several cases report fatalities of humans and animals. The present study is the first to examine the effects of EG on the survival, developmental rate and morphology of two blowfly species, (Diptera: Calliphoridae) typically found on corpses and carcasses: Lucilia sericata (Meigen) and L. cuprina (Wiedemann). Both species were reared on substrates (beef liver) spiked with three different concentrations of EG that could cause death in either a human or cat: 1/2LD₅₀ (T1), LD₅₀ (T2), 2LD₅₀ (T3), in addition to a control treatment (C) with no EG. Results of this research show that: a) both species are unable to survive if reared on a food substrate spiked with the highest concentration of EG (T3), while lower and medium concentrations (T1, T2) affect, but not prevent, the survival and the completion of the life cycle of such species; b) adults of L. sericata eclose only in C and T1, while adults of L. cuprina in both C, T1, T2; however, c) the developmental time of both species reared in T1 and T2 is statistically slower than the control; d) the body length of the immatures of both of the species reared in T1 and T2 is statistically smaller than the control.