Effect of body mass and clothing on decomposition of pig carcasses

Diet and rate of decomposition of the corpse in a human surrogate

The decomposition of an inert body seems to depend on the physiological, biological and physical characteristics of the corpse. The effect of these, especially of extra-biological mechanisms, on the rate of decomposition of the corpse does not seem to be sufficiently explored. The present work proposes to examine the influence of the type of feeding on the rate of cadaver decomposition in a human surrogate. It is based on a sample of four corpses of juvenile male pigs of the species Sus scrofa domesticus, three of which are experimental and one is a control aged 12 weeks and having a mass between 19 and 24 kg. The three experimental pigs were fed an energetic, construction and functional diet respectively. The control was fed a general diet. These different carcasses are exposed to the open air on four similar sites. The experiment is repeated twice, according to the protocol that guided the initial experiment conducted on comparable sites (eight cadavers, six experimental and two control). The measurement of the pigs' diet was done through a questionnaire. The mass of the decomposing carcass was explored by a specific tool, in this case, the weighing device. The results show that the rate of decomposition of the cadaver of pigs fed a general diet is higher than that of the cadavers of their counterparts fed construction, functional or energy diets. The type of diet would therefore influence the rate of decomposition of the cadaver of a human surrogate.

Field validation of post-mortem interval estimation based on insect development. Part 1: Accuracy gains from the laboratory rearing of insect evidence

There is a consensus that forensic methods must be valid. The high quality of the method may be fully demonstrated only through validation. Unfortunately, there are very few experimental or casework validations of entomological methods for estimating post-mortem interval (PMI). Here, we present the first part of the results from the field validation of minimum PMI (PMImin) estimates based on insect development. From eight pig carcasses (24-46.4 kg) exposed in a forest habitat of Western Poland, one every one or two months, we collected insect evidence with standard entomological techniques. Using weather station temperatures and the thermal summation method, PMImin was estimated based on insect life stages that were reared under controlled laboratory conditions. Through rearing an insect until the next developmental landmark (or until eclosion), its age at the time of collection (and eventually PMImin) may be estimated by subtracting thermal accumulation in the laboratory from the corresponding thermal constant. We hypothesized that rearing insect evidence significantly improves the accuracy of PMImin compared to the estimation based on non-reared insect evidence. The results clearly supported this hypothesis. However, the accuracy significantly increased only in the case of these insects that developed normally during rearing. When their development in the laboratory was prolonged, PMImin was significantly less accurate. For the normal development sample the accuracy improved in all species and life stages. The largest accuracy gains from rearing were recorded for Calliphora vomitoria (Diptera: Calliphoridae) and Stearibia nigriceps (Diptera: Piophilidae). Moreover, when puparia or third instar larvae were reared, gains were larger than in the case of earlier life stages. In conclusion, this study demonstrated that the method of rearing insect evidence to improve the accuracy of PMImin is valid. However, it needs to be used with caution, since substantial part of the evidence may die or slow down their development in the laboratory, which violates assumptions of the method.

Forensic experiments on animal scavenging: A systematic literature review on what we have and what we need

Vertebrate scavengers frequently affect forensic casework by feeding on human remains or by scattering body parts and bones. Therefore, animal activity can influence complete recovery of bodies, trauma analysis, and the estimation of the postmortem interval (PMI), potentially hampering identification of the deceased and elucidation of the perimortem circumstances. Experimental research is well suited to investigate scavengers and their impact on carcasses over time, generating knowledge on the forensic relevance of certain scavenger species or communities. However, there are currently no systematised standards to conduct these investigations with a forensic focus, impeding comparison and synthesis of the studies. In our work, we performed a systematic literature review and found 79 publications featuring terrestrial experiments on vertebrate scavenging and/or scattering within a forensic context. We extracted 21 variables describing the study environment, experimental design and the specimens. The results show that there is considerable inconsistency in the study designs and that some of the variables are insufficiently reported. We point out research questions and areas that require attention in future studies, stressing the importance of infrequently mentioned or applied variables. Furthermore, we recommend guidelines to include and report a list of variables in forensic scavenging and scattering experiments. These guidelines will help standardising future research in the field, facilitating inter-study consolidation of results and conclusions, and consequently, inform forensic casework.

The Future Is Now: Unraveling the Expanding Potential of Human (Necro)Microbiome in Forensic Investigations

The relevance of postmortem microbiological examinations has been controversial for decades, but the boom in advanced sequencing techniques over the last decade is increasingly demonstrating their usefulness, namely for the estimation of the postmortem interval. This comprehensive review aims to present the current knowledge about the human postmortem microbiome (the necrobiome), highlighting the main factors influencing this complex process and discussing the principal applications in the field of forensic sciences. Several limitations still hindering the implementation of forensic microbiology, such as small-scale studies, the lack of a universal/harmonized workflow for DNA extraction and sequencing technology, variability in the human microbiome, and limited access to human cadavers, are discussed. Future research in the field should focus on identifying stable biomarkers within the dominant Bacillota and Pseudomonadota phyla, which are prevalent during postmortem periods and for which standardization, method consolidation, and establishment of a forensic microbial bank are crucial for consistency and comparability. Given the complexity of identifying unique postmortem microbial signatures for robust databases, a promising future approach may involve deepening our understanding of specific bacterial species/strains that can serve as reliable postmortem interval indicators during the process of body decomposition. Microorganisms might have the potential to complement routine forensic tests in judicial processes, requiring robust investigations and machine-learning models to bridge knowledge gaps and adhere to Locard's principle of trace evidence.

Subaerial Decomposition of Small-Sized Remains in The Netherlands: Important Findings Regarding the PMI of a Four-Year Taphonomic Study

Studying post-mortem changes based on signs of decomposition (e.g., using scoring models) is one of the methods used in scientific studies to relate observable changes to the post-mortem interval (PMI). The majority of the studies on cadaver decomposition are based on large cadavers. There is limited literature on the decomposition pattern and rate of small cadavers, even though it is at least as important to be able to estimate the PMI for infants and subadults. Therefore, it is crucial to acquire knowledge of the decomposition process of child-sized remains. To fill this knowledge gap, a season-based subaerial outdoor decomposition study was conducted with small pig cadavers at the Forensic Anthropological Outdoor Research Facility located in Den Ham, The Netherlands, over a period of 4 years. Den Ham is located in the eastern part of the Netherlands, close to the German border, and has a temperate maritime climate, with a Cfb classification according to the Köppen-Geiger system. Salient findings were acquired during the decomposition study, specifically regarding a deviating decomposition rate during winter and the subsequent spring, reproducibility, the effect of body weight, post-mortem movement, the effect of heavy rainfall on insect activity, delayed bloating, the interaction of different insect species, and invertebrate activity. This article includes a systemic review of the results obtained during this four-year decomposition study and discusses the impact of the findings on the estimation of the PMI.

A synthesis of carcass decomposition studies conducted at a tropical (Aw) taphonomy facility: 2013-2022

Decomposition studies have been conducted in several regions of the world, but relatively few have investigated taphonomy in tropical environments. Even fewer have explored carcass decomposition during multiple tropical seasons, leaving the relationships between season and decomposition in tropical environments poorly understood. Ten decomposition studies using 30 carcasses were conducted in Honolulu, Hawaii, USA to start addressing this knowledge gap. These studies show that some postmortem processes were observed regardless of season. Carcass temperature and chemistry were spatiotemporally variable. Fly larval masses were consistently observed within 3 days (∼75 ADD) postmortem and carcasses lost 60%-90% of mass by 10 days (∼250 ADD) postmortem (Total Body Score ∼26). Season had a significant effect on decomposition, yet the warmest and most humid seasons did not always result in the most rapid and extensive decomposition. Seasonal variation appears to be less pronounced than at other tropical decomposition sites.

Estimation of Late Postmortem Interval: Where Do We Stand? A Literature Review

Estimating time since death can be challenging for forensic experts, and is one of the most challenging activities concerning the forensic world. Various methods have been assessed to calculate the postmortem interval on dead bodies in different stages of decomposition and are currently widely used. Nowadays, the only well-recognized dating technique is carbon-14 radioisotope measurement, whereas other methods have been tested throughout the years involving different disciplines with different and sometimes not univocal results. Today, there is no precise and secure method to precisely determine time since death, and late postmortem interval estimation remains one of the most debated topics in forensic pathology. Many proposed methods have shown promising results, and it is desirable that with further studies some of them might become acknowledged techniques to resolve such a difficult and important challenge. The present review aims at presenting studies about the different techniques that have been tested in order to find a valuable method for estimating time since death for skeletal remains. By providing a comprehensive overview, the purpose of this work is to offer readers new perspectives on postmortem interval estimation and to improve current practice in the management of skeletal remains and decomposed bodies.

Fauna of flies (Diptera) on bones and emergence succession: Forensic implications in skeletal remains

Fauna of flies on pig carcasses and bones and their emergence succession were investigated in Hokkaido, Japan. A total of 55,937 flies consisting 23 identified species in 16 families was collected from emergence traps after removal of carcasses and emergence containers containing bones. In emergence traps, Lucilia caesar (Linnaeus) emerged earliest, followed by Hydrotaea ignava (Harris). Piophilid flies emerged 22-25 days later than L. caesar, and their emergence periods were prolonged. In emergent flies from bones, Piophilidae was the dominant family, comprising five species; Stearibia nigriceps (Meigen) was the most abundant, followed by Liopiophila varipes (Meigen) and Protopiophila latipes (Meigen). Stearibia nigriceps and L. varipes remarkably dominated in summer bones and overwintering spring bones, respectively. Piophilids emerged from all 11 types of bones; the thoracic spine significantly yielded the most numerous individuals in S. nigriceps. The developmental duration of larvae of S. nigriceps in bones was estimated to be 12-34 days after placement of carcasses in summer. Observations of overwintering bones showed that L. varipes and Centrophlebomyia grunini (Ozerov) overwintered in larvae inside of bones. The importance of examining piophilid larvae in bones and their potential forensic usefulness are discussed.

Mummification in a forensic context: an observational study of taphonomic changes and the post-mortem interval in an indoor setting

The objective of this study was to evaluate the presence of mummification in an indoor setting, with an emphasis on the forensic perspective. A dataset of 102 forensic autopsy cases was assessed for distribution of desiccation of skin and soft tissue (i.e., subcutaneous fat and musculature) and for moist decompositional (i.e., putrefactive) changes. Further, possible correlation with the post-mortem interval (PMI) was evaluated, as well as the effects of clothing coverage of the body. The results indicated that yellow to orange parchment-like desiccated skin was found at significantly shorter PMIs than reddish brown to black leathery desiccated skin, even when soft tissue desiccation was included in the comparative analysis. Clothing appeared to have a significant decelerating effect on the extent of desiccation on the legs, but findings in regard to whole body or torso/arms were inconclusive. A large variation in PMIs was evident as regards fully desiccated skin (PMI 18-217 days), indicating difficulties in PMI estimation due to a variable repressive effect on the decompositional process per se in an indoor setting. For the specific case in forensic practice, no definite conclusion can be drawn from the observed desiccation changes to the PMI. One way forward might be creating a systematic and standardized method for describing different desiccation types, as well as other cooccurring decompositional changes and how they relate to the PMI, as a foundation for a future quantification model.

A Preliminary Study of Body Decomposition and Arthropod Succession in an Arid Area in Northwest China During Summer

The study of insect fauna and their development and succession patterns on decaying cadavers is crucial to promoting insect evidence as a useful tool in forensic science, particularly for estimating the postmortem interval (PMI). Body decomposition and arthropod succession are affected by many factors and exhibit substantial regional variations; therefore, detailed succession studies in different biogeographic regions are required for understanding the successional patterns of insects in various environments. This study was conducted in the summer of 2021 using three domestic pig carcasses (Sus scrofa domestica L., 1758) in the field of Shizuishan City, Ningxia, Northwest China. A total of 40 species of necrophagous insects belonging to three orders and 16 families were collected. Among Diptera, Lucilia sericata (Meigen,1826), Chrysomya megacephala (Fabricius,1794), and Phormia regina (Meigen,1826) (Diptera: Calliphoridae) were the dominant species. As for Coleoptera, the dominant species changed throughout the process of carcass decomposition from Saprinus semipunctatus (Fabricius,1792) (Coleoptera: Histeridae) to Dermestes maculatus DeGeer,1774 and Dermestes frischii Kugelann,1792 (Coleoptera: Dermestidae). The carcasses desiccated rapidly and reached the remains stage under extreme conditions of high temperatures and low humidity, after which a large amount of dried tissue of the carcasses attracted populations of Coleoptera, particularly Dermstidae, which were abundant and remained until the end of the experiment on day 50. The current study is the first forensic entomological investigation of succession in Northwest China and provides basic data for the estimation of PMI during summer in this region.

Investigating the Timing and Extent of Juvenile and Fetal Bone Diagenesis in a Temperate Environment

It is well understood that intrinsic factors of bone contribute to bone diagenesis, including bone porosity, crystallinity, and the ratio of organic to mineral components. However, histological analyses have largely been limited to adult bones, although with some exceptions. Considering that many of these properties are different between juvenile and adult bone, the purpose of this study is to investigate if these differences may result in increased degradation observed histologically in fetal and juvenile bone. Thirty-two fetal (n = 16) and juvenile (n = 16) Sus scrofa domesticus femora subject to different depositions over a period of two years were sectioned for histological observation. Degradation was scored using an adapted tunneling index. Results showed degradation related to microbial activity in both fetal and juvenile remains across depositions as early as three months. Buried juvenile remains consistently showed the greatest degradation over time, while the blanket fetal remains showed more minimal degradation. This is likely related to the buried remains’ greater contact with surrounding soil and groundwater during deposition. Further, most of the degradation was seen in the subendosteal region, followed by the subperiosteal region, which may suggest the initial microbial attack is from endogenous sources.

Histological changes in lingual striated muscle tissue of human cadavers to estimate the postmortem interval

Although there are physiological methods to determine the postmortem interval (PMI), interval forensic histopathology can be applied to obtain accuracy. The aim was to describe the histological changes in human lingual striated musculature at different PMI. Seven groups were formed according to increasing PMI of 6, 12, 24, 48, 72, 96 and 120 h postmortem (PM). Each group was made up of 16 samples of tongues from each cadaver. The samples were fixed in buffered formaldehyde at 10% and processed for embedding in paraplast. Section 5 μm thick were cut and dyed with H&E for analysis. The study was approved by the Bioethics Committee of the Universidad San Francisco de Quito, Ecuador. The histological changes in the striated muscle cells of the tongue were associated with the different PMI. From 6 to 24 h PM, there were initial changes in the cellular and nuclear morphology. At 48 h PM, at least 50% of the samples presented poorly conserved and reduced muscle striations. At 72 h PM, 100% of the cases presented myofibers with altered morphology, cytoplasmic vacuoles (93.75%), edema (68.55%) and pyknosis (93.75%). At 96 and 120 h PM, the myofibers presented pyknotic nuclei, and they were absent in the rest. The changes in the histology of the human lingual striated muscle make it possible to estimate the PMI, either in the early phase (0-72 h) or the late phase (92-120 h). However, further research is needed to verify, refine and expand on these results.

Thick quilt may severely impact the estimation of postmortem interval using forensic entomology-based methods -two case reports

This paper introduces two indoor cases in China, characterized by bodies lying on a mattress, covered with thick quilts and wearing clothes. There were obvious deviation in the estimated minimum postmortem interval (PMI_min) of the corpses using entomological methods. Based on the forensic entomology evidence from the scene, the PMI_min estimated using temperature data from the nearest weather station was longer than the actual postmortem interval (PMI) based on the police investigation and the security camera footage. The most probable cause of the errors in PMI_min estimation was the hindrance in heat dissipation since the corpses were covered with thick quilts while lying on the mattress. Therefore, the heat generated by the decomposition process and larval activity was hard to lose, resulting in the rapid development of insects. These case reports emphasize the importance of temperature collection in forensic entomological investigations. Our findings call for standardized temperature acquisition procedures, including which temperature measurements (body, microenvironment or ambient temperature) should be used in forensic entomological investigations when handling similar cases.

Initial laboratory validation of temperature development models for Necrodes littoralis L. (Staphylinidae: Silphinae)

Development models of necrophagous insects are applied in forensic entomology for post-mortem interval estimation. Such estimates may be used as scientific evidence in legal investigations. For this reason, it is important that the models are valid and that the expert witness is aware of their limitations. Necrodes littoralis L. (Staphylinidae: Silphinae) is a necrophagous beetle species that frequently colonizes human cadavers. Temperature models of development for the Central European population of these beetles were recently published. In this article, we present results of the laboratory validation study for these models. Errors of beetle age estimation differed significantly between the models. Thermal summation models yielded the most accurate estimates, and the isomegalen diagram least accurate estimates. Errors of the beetle age estimation varied across beetle developmental stages and rearing temperatures. In general, most development models of N. littoralis were satisfactorily accurate in estimating beetle age under laboratory conditions; therefore, the study provides initial evidence to support their validity in forensic cases.

Evaluation of Muscle Proteins for Estimating the Post-Mortem Interval in Veterinary Forensic Pathology

Postmortem cadaveric changes are commonly used to estimate the postmortem interval (PMI) in humans and animals. However, these modifications have been poorly investigated in animals of interest to veterinary forensic pathology. The aim of this study was to investigate the potential use of muscle proteins (desmin and dystrophin) as biomarkers for estimating the PMI in dogs. For this study, 10 dead adult dogs were evaluated for 4 days in a temperature-controlled room at 19 ± 1 °C. For each animal, at 3, 24, 48, 72, and 96 h after death, a 1 × 1 × 1 cm cube of muscle tissue was removed from the vastus lateralis and triceps brachii. Protein expression levels were analyzed by immunohistochemical examination and immunoblot analysis. The obtained results showed rapid dystrophin degradation, with complete disappearance at 72 h after death. In contrast, desmin-positive fibers and desmin protein bands detected by immunoblot were observed on all 4 days of observation. Our findings suggest the potential use of muscle proteins as biomarkers for estimating the PMI in dogs.

Carcass appearance does not influence scavenger avoidance of carnivore carrion

The selection or avoidance of certain carrion resources by vertebrate scavengers can alter the flow of nutrients in ecosystems. Evidence suggests higher trophic level carrion is scavenged by fewer vertebrate species and persists longer when compared to lower trophic level carrion, although it is unclear how scavengers distinguish between carcasses of varying species. To investigate carnivore carrion avoidance and explore sensory recognition mechanisms in scavenging species, we investigated scavenger use of intact and altered (i.e., skin, head, and feet removed) coyote-Canis latrans (carnivore) and wild pig-Sus scrofa (omnivore) carcasses experimentally placed at the Savannah River Site, SC, USA. We predicted carnivore carcasses would persist longer due to conspecific and intraguild scavenger avoidance. Further, we hypothesized visually modifying carcasses would not reduce avoidance of carnivore carrion, given scavengers likely depend largely on chemical cues when assessing carrion resources. As expected, mammalian carnivores largely avoided scavenging on coyote carcasses, resulting in carnivore carcasses having longer depletion times than wild pig carcasses at intact and altered trials. Therefore, nutrients derived from carnivore carcasses are not as readily incorporated into higher trophic levels and scavengers largely depend on olfactory cues when assessing benefits and risks associated with varying carrion resources.

Dental DNA as an Indicator of Post-Mortem Interval (PMI): A Pilot Research

Teeth have proven to be a reliable source of DNA for forensic analysis as the pulp is rich in cells and protected from damaging factors and contamination by dental hard tissues. The pilot study aims to evaluate the feasibility of Next-Generation sequencing analysis on dental pulp to detect genetic mutations in DNA caused by post-mortem cell necrosis. We used a 56-gene oncopanel kit on a sample of 17 teeth extracted from living patients. Time of the tooth avulsion was assumed as death of the individual and Post-mortem Interval (PMI) was the time elapse since the DNA extraction and analysis. Days and Accumulated Degree Days (ADD) were assumed as measures of PMI that ranged between 0 to 34 days. Only 38 of the 56 considered genes proved to be affected by mutations (101), thus being of forensic interest. More specifically, 14 mutations occurred only in a specific range of PMIs/ADD; 67 were detected (alone or as clusters of the same gene) at specific PMI/ADD; 22 occurred at every PMI/ADD, except for some specific intervals. Since dental pulp was not targeted by any oncological diseases and all teeth were intact, vital, and from patients with unremarkable medical history, it could be assumed that mutations were due to post-mortem DNA changes induced by pulp death and the increasing time elapse since death. This pilot study found encouraging results in the application of NGS analysis on dental DNA, especially for PMIs of several days for which the traditional tools for PMI estimation have limitations. Further research on a larger sample of PMI and validation research on a larger sample of PMI and validation of the results are indeed necessary.

Temperature models of development for Necrodes littoralis L. (Coleoptera: Silphidae), a carrion beetle of forensic importance in the Palearctic region

Analysis of insects can provide evidence in death cases, for example, by answering the question about the time of death. Apart from flies, beetles are the second most useful insect group in forensic entomology. To elucidate the time of death based on insect evidence, developmental models of a given species are necessary. In this study, we developed such models for Necrodes littoralis, a necrophagous beetle, which is common in the Palearctic region and has great potential in forensic entomology. We monitored the development at 10 constant temperatures (14–30 °C). Larvae were reared in aggregations. Thermal summation models, isomorphen and isomegalen diagrams and growth curves were derived using the data. Depending on the temperature, development lasted between about 23 and 89 days. Mortality was high at the extremes of the temperature range. The thermal summation constant for the total development was 434.7 ± 28.86 accumulated degree-days above a developmental threshold of 9.04 ± 0.55 °C. This is the first comprehensive dataset on the development of N. littoralis. Implications for its use in forensic casework are discussed.

Death in the paddy field: Carcass decomposition and associated arthropods in subunits of a rice field landscape

Although rice production landscapes are often the scene of homicides, vertebrate decomposition and associated arthropods have never been described from rice paddies. Tropical rice landscapes are typically composed of irrigated/non-irrigated rice fields, fallow land (i.e., uncultivated fields), and low earthen levees (bunds) used as access pathways. The specific microclimatic and environmental conditions associated with each subunit of rice field landscapes are likely to impact carcass decomposition as well as the arthropod species associated with carrion. Here, we tested the hypothesis that the combined effects of constraints on arthropod colonization and survival, scarcity of necromass, limited habitat architecture, and recurrent disturbance limit the ability of carrion-related arthropods to colonize corpses and large carcasses in tropical rice-fields. Our results from monitoring pig carcasses in Philippine rice fields indicated that vertebrate decomposition in irrigated fields was slower and incomplete when compared to non-irrigated fields and bunds. Carcasses were colonized by a small complex of carrion-related arthropods that differed in composition and relative species abundance between dry bunds and relatively humid rice paddies. Fire ants (Solenopsis germinata) were observed frequently on carcasses exposed on bunds, rarely in non-irrigated fields, and almost never in irrigated fields. The presence of fire ants was associated with reduced blow fly (Chrysomya megacephala) abundance. Taken together, this indicates that the arthropod fauna associated with carcasses in tropical rice fields is relatively simple in contrast to the generally high arthropod diversity reported for other ecosystems at tropical latitudes. The limited richness of the community also means that an understanding of the development of one abundant calliphorid blow fly, C. megacephala, may be sufficient to investigate deaths and homicides under conditions similar to the ones described in this study.

Estimating the Postmortem Interval of Carcasses in the Water Using the Carrion Insect, Brain Tissue RNA, Bacterial Biofilm, and Algae

The accurate estimation of postmortem interval (PMI) is crucial in the investigation of homicide cases. Unlike carcasses on land, various biological and abiotic factors affect the decomposition of carcasses in water. In addition, the insect evidence (e.g., blow flies) that is commonly used to estimate the PMI are unavailable before the carcasses float on water. Therefore, it is difficult to estimate the PMI of a carcass in water. This study aimed to explore an effective way of estimating the PMI of a carcass in water. Carrion insects, brain tissue RNA, bacterial biofilm on the skin surface, and algae in water with PMI were studied using 45 rat carcasses in a small river. The results showed that carrion insects might not be suitable for the estimation of PMI of a carcass in water since they do not have a regular succession pattern as a carcass on land, and the flies only colonized six of the carcasses. The target genes (β-actin, GAPDH, and 18S) in the brain tissue were associated with the PMI in a time-dependent manner within 1 week after death. A polynomial regression analysis was used to assess the relationship between the gene expression profiles and PMI. The correlation coefficient R² of each regression equation was ≥ 0.924. A third-generation sequencing analysis showed that the bacteria on the skin surface of the carcass and the algae in the water samples around the carcass had a regular succession pattern, where Cryptomonas and Placoneis incased and decreased, respectively, within first 9 days. The results of this study provide a promising way to use the brain tissue RNA, bacterial biofilm, and algae to estimate the PMI of a carcass in water.

How does mass loss compare with total body score when assessing decomposition of human and pig cadavers?

Providing accurate and reliable measures of decomposition is paramount for forensic research where decomposition progress is used to estimate time of death. Mass loss is routinely used as a direct measure of biomass decomposition in ecological studies, yet few studies have analysed mass loss in a forensic context on human cadavers to determine its usefulness for modelling the decomposition process. Mass loss was examined in decomposing human and pig cadavers, and compared with other common decomposition metrics, such as total body score (TBS). One summer and one winter field decomposition experiment was conducted using human and pig cadavers, as pigs are often used as proxies for human cadavers in forensic research. The two measures of decomposition revealed two contrasting patterns of decomposition on pigs and humans, particularly in winter where TBS stabilised at similar values, but mass loss differed greatly. Mass loss was found to be faster in pigs than humans during early decomposition. Pigs lost 75% of their mass in winter, while humans lost less than 50%; however, in summer, both lost around 80% of their mass. TBS displayed similar patterns in both experiments, with TBS increasing more rapidly in pigs compared with humans but both eventually reaching similar TBS values in late decomposition. Measuring mass loss can provide additional information about decomposition progress that is missed if using TBS only. Key differences in decomposition progress between cadaver types were also observed, suggesting caution when extrapolating data from pigs to humans for forensic research and decomposition modelling.

Competition of insect decomposers over large vertebrate carrion: Necrodes beetles (Silphidae) vs. blow flies (Calliphoridae)

Large carrion is inhabited by highly variable and interactive communities of insects. Positive interactions in carrion insect communities have been recently the focus in carrion ecology. In contrast, competition between carrion insects is rather undervalued. Here we provide evidence that blow flies (Calliphoridae) and Necrodes beetles (Silphidae), dominant decomposers of large carcasses in terrestrial habitats, compete over carrion. By reanalyzing the results from 90 pig carcasses, we demonstrated that the contribution of the flies and the beetles to the decay was negatively related. The greater part of the large carrion pool was monopolized by blow flies, whereas Necrodes beetles abundantly colonized carcasses, on which blow flies were less effective as decomposers. In behavioral assays, we found that adult beetles killed 4 times more frequently feeding than postfeeding third instar larvae of the flies, with the large decrease in the killing frequency after the larvae reached the age of early third instar. Therefore, adult Necrodes beetles preferentially killed the larvae that were before or in their peak feeding. The study provides evidence that the interaction between blow flies and Necrodes beetles is a combination of indirect exploitative effects of the flies and direct interference effects of the beetles (the mixed competition).

The Effect of Different Coverings on Total Body Score Development of Buried Carcasses

Background

Examination of post-mortem changes is one of the ways to assess decomposition process on buried bodies. Nonetheless, studies on such assessment are still lacking, especially on the effects of body coverings by different materials in burial conditions. The aim of this research is to study the effect of different types of covering towards decomposition on buried rabbit carcasses by using Total Body Score (TBS) system.

Methods

Twenty-seven rabbit carcasses were divided into: (i) No Clothing; (ii) Thick Clothing and (iii) Plastic Wrapping groups, and buried into individual shallow graves. One subject was exhumed from first to ninth post-burial week and assessed by using TBS system.

Results and Discussion

There are significant differences among TBS between different coverings while controlling the time factor, F (2, 23) = 4.80, P < 0.05, partial η² = 0.294. TBS score for Plastic Wrapping group is significantly lower than No Clothing group over times at α = 0.05, P < 0.05. The slightly delaying effect of thick clothing is caused by design of jacket, which allows arthropods access and microbial activity. Relatively strong delaying effect by plastic covering could be caused by impermeable property that caused accumulation of decompositional products and slow down the degradation.

Conclusion

In conclusion, TBS system is a potential tool in describing rate of decomposition for buried cases in Malaysia.

First report of the presence of Necrodes littoralis (L.) (Coleoptera: Silphidae) on a human corpse in Italy

The colonization of a human body by Necrodes littoralis (L.) (Coleoptera: Silphidae) is reported for the first time in Italy. This species is both necrophagous and predator of necrophagous fauna. The body colonized by the coleopteran was found indoors, in an advanced decomposition stage, in a suburban area of Cosenza (Calabria, Southern Italy) in November. Insects (adults, puparia and larvae) were collected on and around the body. Puparia and larvae were raised in the laboratory until the adult stage for morphological identification, which was carried out through taxonomical keys. Besides N. littoralis, also the presence of Calliphora vicina Robineau‐Desvoidy, Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae), Hydrotaea dentipes (Fabricius) (Diptera: Muscidae), and Creophilus maxillosus (L.) (Coleoptera: Staphylinidae) was detected. Necrodes littoralis is a species of forensic interest because it may colonize human and vertebrate corpses and has been reported elsewhere in Europe.

Suitability of specific soft tissue swabs for the forensic identification of highly decomposed bodies

When decomposition of a recovered body is fairly advanced, identification based on common morphologic features is often impossible. In these cases, short tandem repeat (STR) marker genotyping has established itself as a convenient and reliable alternative. However, at very progressed stages of decomposition, postmortem tissue putrefaction processes can decrease DNA yields considerably. Hence, not all types of tissue are equally suitable for successful STR marker-based postmortem identification. Bone or dental material is often analysed in corpses with advanced decompositional changes. However, processing of these materials is very elaborate and time and resource consuming. We have therefore focused on the suitableness of various types of soft tissue swabs, where DNA extraction is easier and faster. By sampling 28 bodies at various stages of decomposition, we evaluated the suitability of different tissues for genotyping at varying degrees of physical decay. This was achieved by a systematic classification of the sampled bodies by morphological scoring and subsequent analysis of multiple tissue swabs of the aortic wall, urinary bladder wall, brain, liver, oral mucosa and skeletal muscle. In summary, we found variable degrees of suitability of different types of soft tissue swabs for DNA-based identification. Swabs of the aortic wall, the urinary bladder wall and brain tissue yielded the best results - in descending order - even at advanced levels of decay.

Post-Mortem Interval Estimation Based on Insect Evidence: Current Challenges

During death investigations insects are used mostly to estimate the post-mortem interval (PMI). These estimates are only as good as they are close to the true PMI. Therefore, the major challenge for forensic entomology is to reduce the estimation inaccuracy. Here, I review literature in this field to identify research areas that may contribute to the increase in the accuracy of PMI estimation. I conclude that research on the development and succession of carrion insects, thermogenesis in aggregations of their larvae and error rates of the PMI estimation protocols should be prioritized. Challenges of educational and promotional nature are discussed as well, particularly in relation to the collection of insect evidence.

Flies Do Not Jump to Conclusions: Estimation of the Minimum Post-Mortem Interval for a Partly Skeletonized Body Based on Larvae of Phromia regina (Diptera: Calliphoridae)

Simple Summary

Many factors can influence the appearance of human remains. In the case presented here, the remains appeared to be exposed for months, because the bones were visible. Fly maggots collected from the body, however, suggested a much shorter period of only about two weeks. The confession of the perpetrator ultimately confirmed the shorter exposure time of the remains.

Abstract

Skeletonization is often perceived as an indicator of long post-mortem intervals. The finding of feeding larvae of first colonizers, on the other hand, indicates days. We present a case in which both findings were present. Larvae of Phormia regina, aged 9 days, and skeletonization of the head and part of the thorax were both found on an unidentified female body. Identification of dentures eventually led to resolution of the case and a confession, which settled the seeming contradiction in favor of forensic entomology.

Comparison of Accumulated Degree-Days and Entomological Approaches in Post Mortem Interval Estimation

Simple Summary

Among the investigative questions to define the temporal frame of a criminal event, the time since death plays a fundamental role. After death, the body goes through a series of physical and chemical transformations—known as decomposition. The way in which different parts of the body undergo these transformations can be quantified with a scale of scores (TBS, the total body score) and used for the time since death evaluation using the accumulated degree-days (ADDs) parameter, which accounts for time and temperature. This method is reported as TBS/ADD. Another way to estimate the time since death is based on the insect development on the body. Flies represent the first body coloniser and the development of their immature stages is used to define the time of colonisation that is temperature dependent and species specific. In this study, the two methods were compared based on 30 forensic cases occurring in northern Italy. The results highlighted the limits of the TBS/ADD method and the importance of the entomological approach, keeping in mind that with insects the colonization time is evaluated. This time is the minimum time since death.

Abstract

Establishing the post mortem interval (PMI) is a key component of every medicolegal death investigation. Several methods based on different approaches have been suggested to perform this estimation. Among them, two methods based their evaluation on the effect of the temperature and time on the considered parameters: total body score (TBS)/accumulated degree-days (ADDs) and insect development. In this work, the two methods were compared using the results of minPMI and PMI estimates of 30 forensic cases occurring in northern Italy. Species in the family Calliphoridae (Lucilia sericata, Calliphora vomitoria and Chrysomya albiceps) were considered in the analyses. The results highlighted the limits of the TBS/ADD method and the importance of the entomological approach, keeping in mind that the minPMI is evaluated. Due to the fact that the majority of the cases occurred in indoor conditions, further research must also be conducted on the different taxa to verify the possibility of increasing the accuracy of the minPIM estimation based on the entomological approach.

Heat production in a feeding matrix formed on carrion by communally breeding beetles

Insects regulate their body temperature mostly behaviourally, by changing posture or microhabitat. Usually they use heat that is already present in the environment. Sometimes, however, they may manipulate the environment to affect, focus or benefit from thermogenesis. Carrion beetles create a feeding matrix by applying to cadaver surface anal or oral exudates. We tested the hypothesis that the matrix, which is formed on carrion by communally breeding beetle Necrodes littoralis L. (Silphidae), produces heat that enhances insect fitness. Using thermal imaging we demonstrate that heat produced in the matrix formed on meat by adult or larval beetles is larger than in meat decomposing without insects. Larval beetles regularly warmed up in the matrix. Moreover, by comparing matrix temperature and larval fitness in colonies with and without preparation of meat by adult beetles, we provide evidence that formation of the matrix by adult beetles has deferred thermal effects for larval microhabitat. We found an increase in heat production of the matrix and a decrease in development time and mortality of larvae after adult beetles applied their exudates on meat in the pre-larval phase. Our findings indicate that spreading of exudates over carrion by Necrodes larvae, apart from other likely functions (e.g. digesting carrion or promoting growth of beneficial microbes), facilitates thermoregulation. In case of adult beetles, this behaviour brings distinct thermal benefits for their offspring and therefore may be viewed as a new form of indirect parental care with an important thermal component.

Social structure defines spatial transmission of African swine fever in wild boar

The spatial spread of infectious disease is determined by spatial and social processes such as animal space use and family group structure. Yet, the impacts of social processes on spatial spread remain poorly understood and estimates of spatial transmission kernels (STKs) often exclude social structure. Understanding the impacts of social structure on STKs is important for obtaining robust inferences for policy decisions and optimizing response plans. We fit spatially explicit transmission models with different assumptions about contact structure to African swine fever virus surveillance data from eastern Poland from 2014 to 2015 and evaluated how social structure affected inference of STKs and spatial spread. The model with social structure provided better inference of spatial spread, predicted that approximately 80% of transmission events occurred within family groups, and that transmission was weakly female-biased (other models predicted weakly male-biased transmission). In all models, most transmission events were within 1.5 km, with some rare events at longer distances. Effective reproductive numbers were between 1.1 and 2.5 (maximum values between 4 and 8). Social structure can modify spatial transmission dynamics. Accounting for this additional contact heterogeneity in spatial transmission models could provide more robust inferences of STKs for policy decisions, identify best control targets and improve transparency in model uncertainty.

The effects of surface variation on the decomposition of pig carcasses

Studies investigating the differential decomposition of remains on different surfaces have been limited to qualitative data. This study statistically analyses the differences in rate and pattern of decomposition between concrete, gravel and grass surfaces. A total of 11 pigs (Sus scrofa domesticus) were used in the study: three for the concrete and gravel surfaces each, and 5 for the grass surface. Results showed that there was no difference in the overall rate of decomposition between surfaces (p > 0.05); however, there were significant differences in the pattern of decomposition. Mummification was observed on all subjects in the study and may have been the reason for the similarities in the decomposition rates between surfaces. The results of this study show that in the intertwined relationship between factors affecting decomposition surface type may be overshadowed by other environmental factors.

A review of experimental design in forensic taphonomy: moving towards forensic realism

Forensic taphonomy as a discipline requires standardization to satisfy Daubert criteria for scientific data to be admissible in court. In response, there has been a shift towards quantification of methodology and estimating the postmortem interval. Despite these advances, there are still biases and limitations within the discipline not explicitly addressed in the early stages of experimental design nor in final published works. In this article, unresolved debates with respect to the conductance and reporting of forensic taphonomic research are reviewed, beginning with the nature of experimental cadavers, human or animal analogues and their body size, and second, the forensic realism of experimental setups, specifically with respect to caging, clothing and number of carcases. Pigs, albeit imperfect, are a good model to gain a general idea of the trends that may be seen in humans in subsequent validation studies in facilities where human donors are available. To date, there is no consensus among taphonomists on the extent of the effect that body mass has on decomposition progression. More research is required with both human cadavers and non-human analogues that builds on our current knowledge of forensic taphonomy to answer these nagging questions. This will enable the discipline to make the reliable assumption that pigs and donor decomposition data can be applied to homicide cases. A suite of experimental design aspects is suggested to ensure systematic and standardized data collection across different biogeoclimatic circumstances to identify and quantify the effects of potential confounding variables. Such studies in multiple, varied biogeographic circumstances with standardized protocols, equipment and carrion will facilitate independent global validation of patterns. These factors are reviewed to show the need for adjustments in experimental design to ensure relevance and applicability of data within locally realistic forensic situations. The initiation of a global decomposition data network for forensic taphonomists is recommended.

Key points

Pigs are a valuable, albeit imperfect, proxy for human decomposition studies.

There are few or conflicting data on effects of carcase size, carrion ecology, exclusion cages and scavengers.

We recommend single, clothed, uncaged carcases for baseline research to reflect regionally specific forensic casework.

Estimation of physiological age at emergence based on traits of the forensically useful adult carrion beetle Necrodes littoralis L. (Silphidae)

The main entomological method for post-mortem interval involves estimation of age for immature insects found on a cadaver. Forensic entomologists frequently use the thermal summation value for the total immature development (K), which is a measure of physiological time needed to complete development of a species (age at emergence). K is highly variable within the species. Its true value for an adult insect may be estimated based on insect traits such as size and sex at maturity. Here, we have tested, if size and sex of adult beetles of Necrodes littoralis may be useful for the estimation of the true K. Necrodes littoralis is a Palearctic carrion beetle that frequently colonizes human cadavers in forest and agricultural environments. General and sex-specific thermal summation models for the emergence and models for the relationship between size of adult beetles and their age at emergence were developed for N. littoralis. The models were subsequently tested in the validation study. The general K for N. littoralis was about 469 (+/-25 SE) accumulated degree-days above the developmental threshold of about 8.5 (+/-0.45 SE) °C. Thermal summation parameters of the sex-specific models revealed minor differences compared to the general model. A true K was negatively related to the beetle size. Methods for the estimation of K represented its true value with different accuracy. The highest accuracy was obtained when K was estimated using beetle weight as a predictor variable and the sex-specific models for the relationship between K and size, although sex contributed slightly to this improvement. Using this method the estimated K represented the true K with the error of 6.3%, while the error for K from the general thermal summation model was about 9.7%. In conclusion, the findings demonstrate that physiological age at emergence of N. littoralis may be accurately predicted based on the adult beetle size. Necrodes littoralis is a second beetle species in which the age at maturity was more accurately represented by size-based estimates of K than K from the general thermal summation model. Therefore, we encourage testing the relationship between K and size in all insect species that are used in forensic entomology; particularly blow flies and flesh flies.

The effect of clothing on decomposition and vertebrate scavengers in cooler months of the temperate southwestern Cape, South Africa

With research providing conflicting results from different habitats across the globe, the effect of clothing on decomposition is unclear; some studies indicate clothing increases decomposition rate by facilitating increased insect activity, and others conclude clothing prolongs the decay process. In South Africa, such research is lacking, with no data for the Western Cape Province, which suffers from a high murder rate with many unclaimed, unidentified bodies. Improving post-mortem interval (PMI) estimates will increase chances of correct forensic identification of decedents by narrowing the search window for police. Since no current PMI estimation method accounts for the possible influence of clothing, this study was designed to examine the effect of seasonally appropriate common clothing on decomposition rate in the thicketed Cape Flats Dune Strandveld, Cape Town, a forensically significant region. Four ∼60 kg domestic pig carcasses (Sus scrofa domesticus) were used as proxies for human decomposition, two were clothed and two unclothed. The clothing, altered by a seamstress to ensure an appropriate fit, caused a notable decrease in decay rate in this initial sample. Daily weight loss was used as a quantitative measure of decomposition progression, as the clothing prevented the use of visual decomposition scoring systems. Weight loss was closely associated with scavenging activity by the Cape grey mongoose (Galerella pulverulenta), with a clear scavenger preference for unclothed carcasses. This suggests that the effect of clothing on decomposition may be better assessed in this environment by examining how scavengers interact with only a single clothed carcass.

Estimating the Postmortem Interval of Wild Boar Carcasses

Knowledge on the postmortem interval (PMI) of wild boar (Sus scrofa) carcasses is crucial in the event of an outbreak of African swine fever in a wild boar population. Therefore, a thorough understanding of the decomposition process of this species in different microhabitats is necessary. We describe the decomposition process of carcasses exposed in cages. Trial 1 compared a wild boar and a domestic pig (Sus scrofa domesticus) under similar conditions; Trial 2 was performed with three wild boar piglets in the sunlight, shade, or in a wallow, and Trial 3 with two adult wild boar in the sun or shade. The wild boar decomposed more slowly than the domestic pig, which shows that standards derived from forensic studies on domestic pigs are not directly applicable to wild boar. The carcasses exposed to the sun decomposed faster than those in the shade did, and the decomposition of the carcass in the wallow took longest. To assess the state of decomposition, we adapted an existing total body scoring system originally developed for humans. Based on our studies, we propose a checklist tailored to wild boar carcasses found in the field that includes the most important information for a reliable PMI estimation.

Avoidance of carnivore carcasses by vertebrate scavengers enables colonization by a diverse community of carrion insects

Carrion resources sustain a complex and diverse community of both vertebrate and invertebrate scavengers, either obligate or facultative. However, although carrion ecology has received increasing scientific attention in recent years, our understanding of carrion partitioning in natural conditions is severely limited as most studies are restricted either to the vertebrate or the insect scavenger communities. Moreover, carnivore carcasses have been traditionally neglected as study model. Here, we provide the first data on the partitioning between vertebrate and invertebrate scavengers of medium-sized carnivore carcasses, red fox (Vulpes vulpes (Linnaeus)), in two mountainous Mediterranean areas of south-eastern Spain. Carcasses were visited by several mammalian and avian scavengers, but only one carcass was partially consumed by golden eagle Aquila chrysaetos (Linnaeus). These results provide additional support to the carnivore carrion-avoidance hypothesis, which suggests that mammalian carnivores avoid the consumption of carnivore carcasses to prevent disease transmission risk. In turn, the absence of vertebrate scavengers at carnivore carcasses enabled a diverse and well-structured successional community of insects to colonise the carcasses. The observed richness and abundance of the most frequent families was more influenced by the decomposition time than by the study area. Overall, our study encourages further research on carrion resource partitioning in natural conditions.

How reliable is the charred body scale? An interobserver reliability study on scoring burned remains

The error rates of forensic techniques need to be evaluated. The charred body scale is a method for quantifying the level of decomposition in burned remains. 51 files containing photographs of burned pigs at different stages of decomposition were scored by nine participants. Each pig in the photographs was uniformly burned to a different level (Crow Glassman Scale levels 1 to 3). The Crow Glassman Scale describes five levels of burns that include singing of hair and epidermal blistering (CGS level 1) up to complete cremation of the body reducing it to ash (CGS level 5). The three CGS levels were selected to isolate potential scoring errors that may be caused by different burn levels (not accounted for in the development of the charred body scale). Each of the 51 photograph files was scored by participants using the charred body scale as if it were a unique forensic case at an unknown initial burn level and decomposition stage. Interobserver error, hence reliability, of the scores was tested using individual and average absolute agreement interclass correlations. The charred body scale is reliable for remains burned to a Crow Glassman Scale level 1 but not in higher burn levels. It is suggested that a universal scoring method be developed that accounts for multiple burn levels in a single case.

Towards Quantifying Carrion Biomass in Ecosystems

The decomposition of animal biomass (carrion) contributes to the recycling of energy and nutrients through ecosystems. Whereas the role of plant decomposition in ecosystems is broadly recognised, the significance of carrion to ecosystem functioning remains poorly understood. Quantitative data on carrion biomass are lacking and there is no clear pathway towards improved knowledge in this area. Here, we present a framework to show how quantities derived from individual carcasses can be scaled up using population metrics, allowing for comparisons among ecosystems and other forms of biomass. Our framework facilitates the generation of new data that is critical to building a quantitative understanding of the contribution of carrion to trophic processes and ecosystem stocks and flows.

Influence of Clothing on Decomposition and Presence of Insects on Rabbit Carcasses

The decomposition rate and insects attraction to carcasses are affected by a number of factors such as temperature, body mass, the presence of poisons, humidity, and insect activity. The present study was planned to investigate the influence of clothing on both the decomposition process and the presence of insects on rabbit carcasses. The study was performed in May 2016 and involved the use of 18 live mature rabbits (Oryctolagus cuniculus L.), which were euthanized by chloroform. Rabbit carcasses were divided into three replicates with six rabbits in each replicate. Rabbits in each replicate were further subdivided, so that three rabbits were wrapped with cloth, whereas the remaining three were left unclothed. Both clothed and unclothed carcasses reached the dry stage within 6 d. The results of this study showed that clothes neither affect the decomposition process nor the presence of insects (flies and beetles). The pattern of flies and beetles, however, did vary significantly in the different decomposition stages. In total, 2,849 insects, including 2,459 flies and 390 beetles, were collected and sorted during the decomposition process. Among the dominant species, flies were assigned to the families Calliphoridae and Muscidae, whereas beetles were assigned to the families Dermestidae and Histeridae. Lucilia sericata Meigen, Musca domestica L., Dermestes maculatus DeGeer, and Saprinus moyses Marseul were the most abundant species occurring on both the clothed and unclothed carcasses. In conclusion, this study emphasized that, the clothes have no effect when dealing with decay process and insect attraction to the carrions.

Pigs vs people: the use of pigs as analogues for humans in forensic entomology and taphonomy research

Most studies of decomposition in forensic entomology and taphonomy have used non-human cadavers. Following the recommendation of using domestic pig cadavers as analogues for humans in forensic entomology in the 1980s, pigs became the most frequently used model cadavers in forensic sciences. They have shaped our understanding of how large vertebrate cadavers decompose in, for example, various environments, seasons and after various ante- or postmortem cadaver modifications. They have also been used to demonstrate the feasibility of several new or well-established forensic techniques. The advent of outdoor human taphonomy facilities enabled experimental comparisons of decomposition between pig and human cadavers. Recent comparisons challenged the pig-as-analogue claim in entomology and taphonomy research. In this review, we discuss in a broad methodological context the advantages and disadvantages of pig and human cadavers for forensic research and rebut the critique of pigs as analogues for humans. We conclude that experiments using human cadaver analogues (i.e. pig carcasses) are easier to replicate and more practical for controlling confounding factors than studies based solely on humans and, therefore, are likely to remain our primary epistemic source of forensic knowledge for the immediate future. We supplement these considerations with new guidelines for model cadaver choice in forensic science research.

Long-term insect successional patterns on pig carcasses in central Spain

Baseline data on the insect successional patterns on carcasses can be a valuable estimation tool in the investigations of suspicious deaths, particularly when the post-mortem interval is longer than months or years. However, although carrion insect succession is a recurrent topic in forensic science research, the duration of the published studies is typically shorter than 1 year, with only one published study from central Europe documenting successional patterns beyond the first year of decomposition. We provide here the first data on the long-term insect successional patterns in southern Europe, using pig carcasses exposed in the four seasons of the year and documenting the carrion entomofauna during the second and third year of decomposition. Our results confirmed previous observations from central Europe that several Coleoptera species are able to recolonize cadavers during the second and third year after death, with their larvae residing on the remains for long periods. The season of cadaver exposure appears to be a main factor determining the composition of the insect fauna that exploits the remains during subsequent years. Our results suggest that it might be possible to estimate the year and season of death analyzing the composition of the insect fauna occurring on a cadaver. The present data highlight the need for further studies on the long-term insect succession on cadavers in different seasons and geographical areas, in order to fully understand its patterns and ensure its proper application in PMI estimations.