A BASIC algorithm for calculating the postmortem interval from arthropod successional data.

A computer algorithm, implemented in the BASIC language, is presented for calculating the postmortem interval (PMI) from arthropod successional data. Entomology-assisted determination of the PMI promises to be a reliable technique in cases of homicide, suicide, accidental death, and unattended death due to natural causes. The program requires, as input, the identity of arthropod taxa recovered from human remains in a death scene investigation and machine-readable data on carrion-associated arthropod taxa and their known successional patterns of activity for the same geographical area. The program performs rapid comparisons of these lists and, on output, calculates an upper and lower estimate of the PMI, identifies the definitive taxa for these limits, and determines if the remaining corpse taxa have known successional patterns that are consistent for this estimate. An alternate output is provided if one or more corpse taxa do not overlap all the others at any single time in the succession. In that event, the user is prompted to recheck the identity of the non-overlapping taxon or taxa or reevaluate the environmental circumstances surrounding the case in question. Results of the analysis are saved to an ASCII file for output to a printer for making paper copies useful for the entomologist's Case Study Final Report. This program may make possible wider use of this technique in law enforcement and medical investigator offices that utilize both forensic entomologist expertise and IBM PCs (or compatible computers).     

A brief history of forensic entomology.

Apart from an early case report from China (13th century) and later artistic contributions, the first observations on insects and other arthropods as forensic indicators were documented in Germany and France during mass exhumations in the late 1880s by Reinhard and Hofmann, whom we propose recognizing as co-founders of the discipline. After the French publication of Mégnin's popular book on the applied aspects of forensic entomology, the concept quickly spread to Canada and the US. At the time, researchers recognized that the lack of systematic observations of forensically important insects stood in the way of their use as indicators of postmortem interval. General advances in insect taxonomy, and ecology helped close this gap over the following decades.Many early case reports dealt with alleged child homicides, including the suspected use of sulphuric acid. In this context, it was shown that ants, cockroaches, and freshwater arthropods could produce postmortem artifacts suggestive of child abuse.After the World Wars, few forensic entomology cases entered the scientific literature. From the 1960s to the 1980s, Leclecq and Nuorteva were primarily responsible for maintaining the method in Central Europe, with a focus on case work. Since then, basic research in the US, Russia and Canada has opened the way to the routine use of entomology in forensic investigations. The following article gives a brief overview of historic developments in the field. A major focus is on the work done between 1850 and 1950. Since sources from that time remain difficult to track down, the article also includes a historic bibliographical overview on forensic entomology of that era.     

Spectroscopic determination of skin viability. A predictor of postmortem interval

We have demonstrated that skin viability decreases at a measurable rate following death in an animal model. The decreased skin viability was measured by fluorescein diacetate and ethidium bromide using fluorescence emission spectroscopy. There is significant decrease of the fluorescence intensity of the fluorescein diacetate assay between the 1-4 h, the 6-24 h, and the >40 h time points postmortem. For times between 6-24 h and >40 h postmortem the ethidium bromide assay showed consistent and significant increases in signal. The fluorescence measurements in this study showed that under the experimental conditions the time of death could be determined for <4, 6-24, and >40 hapotmotrem. The application of these assays in the field will require further study of the environmental factors.     

Use of beetles in forensic entomology.

Beetles (Coleoptera) have been recognised as providing significant entomological evidence in the medico-legal field, particularly with reference to dry human skeletal remains in the later stages of decomposition.The Dermestidae (skin beetles) and Cleridae (bone beetles) have been found as the most common types infesting exposed human remains and providing evidence in estimating the minimum postmortem interval (PMI).     

A model for the aging of fly larvae in forensic entomology

A method is described for determining the time of hatching of blowfly larvae on a corpse with respect to temperature. Temperature is known to have a profound effect on the rate of growth of fly larvae, and it is suggested that past assumptions that the growth of larvae found in a corpse has taken place at one approximated ambient temperature may have led to large overestimates of the development time of the larvae, and thus overestimates of time of death. Larvae of Lucilia cuprina, Calliphora vicina (= erythrocephala), Calliphora stygia and Calliphora hilli were cultured under constant temperatures, and their growth rates modeled with a logistic growth curve. Two programmes have been developed, one to compute the parameters for the logistic equations, the other is used to estimate the time elapsed from the time at which a sample is removed from a body to the estimated hatching time of the larvae comprising the sample, with temperatures and species as variables.     

Forensic entomology exemplified by a homicide. A combined stain and postmortem time analysis]

The combined analysis of both ant and blow fly evidence recovered from a corpse, and from the boot of a suspect, suggested that an assumed scenario in a high profile murder case was likely to be true. The ants (Lasius fuliginous) were used as classical crime scene stains that linked the suspect to the scene. Blow fly maggots (Calliphora spec.) helped to determine the post mortem interval (PMI) with the calculated PMI overlapping with the assumed time of the killing. In the trial, the results of the medico-legal analysis of the insects was understood to be crucial scientific evidence, and the suspect was sentenced to 8 years in prison.     

Virtual forensic entomology: improving estimates of minimum post-mortem interval with 3D micro-computed tomography

We demonstrate how micro-computed tomography (micro-CT) can be a powerful tool for describing internal and external morphological changes in Calliphora vicina (Diptera: Calliphoridae) during metamorphosis. Pupae were sampled during the 1st, 2nd, 3rd and 4th quarter of development after the onset of pupariation at 23 °C, and placed directly into 80% ethanol for preservation. In order to find the optimal contrast, four batches of pupae were treated differently: batch one was stained in 0.5M aqueous iodine for 1 day; two for 7 days; three was tagged with a radiopaque dye; four was left unstained (control). Pupae stained for 7d in iodine resulted in the best contrast micro-CT scans. The scans were of sufficiently high spatial resolution (17.2 μm) to visualise the internal morphology of developing pharate adults at all four ages. A combination of external and internal morphological characters was shown to have the potential to estimate the age of blowfly pupae with a higher degree of accuracy and precision than using external morphological characters alone. Age specific developmental characters are described. The technique could be used as a measure to estimate a minimum post-mortem interval in cases of suspicious death where pupae are the oldest stages of insect evidence collected.     

Bone weathering patterns of metatarsal v. femur and the postmortem interval in Southern Ontario

Twenty-five defleshed pig femora and 25 metatarsals were placed outdoors and observed over 291 days to establish: (1) bone weathering patterns for use in estimating time since death in Southern Ontario and (2) whether larger (femora) or smaller (metatarsals) bones provide a better indicator of time since death. Pig hind limbs were observed to determine a timeline for decomposition of soft tissues during the fall and winter. Ambient air temperature, humidity, precipitation, sunlight, soil pH, and freezing and thawing were considered as factors affecting the breakdown of bone. Weathering patterns were observed based on the extent of bleaching, amount of periosteum and soft tissues present, as well as the appearance of greasiness, cracking and flaking of cortical bone. Both entomological activity and climatic conditions affected soft tissue decomposition. Animal activity affected both the process of bone weathering and soft tissue decomposition, causing variability in sample decomposition and bone breakdown. The variation in microenvironment, partially caused by soil composition, introduced variability in bone weathering rates. Four bone weathering stages were established based on patterns observed. Femora proved to be more resilient and showed more degrees of change due to weathering, thus proving to be a better indicator of time since death than metatarsals.     

Survival of submerged blowfly species and their parasitoids: implications for postmortem submersion interval

Pupal survival of three blowfly species, Chrysomya albiceps, Chrysomya megacephala, and Chrysomya putoria (Diptera: Calliphoridae) and the parasitoid species Nasonia vitripennis (Hymenoptera: Pteromalidae) was studied after the pupae were experimentally submerged in water. Non-parasitized pupae at different developmental stages, 0, 24, 48, and 72 h, and parasitized pupae after 3, 8, 10, and 12 days of development were submerged for 6, 24, 48, or 72 h. Control groups for each pupal developmental stage (parasitized or not), which were not submerged, were also observed in order to compare the adult emergence rates. The survival of white pupae (0 h/age) decreased with time of submergence for all three blowfly species, showing the lowest rates compared with other experimental pupa groups. For the three blowfly species, non-parasitized pupae at 24 and 48 h of age showed survival rates above 60%. However, for pupae at 72 h of age, the survival rates decreased with increased underwater time, with less than 30% survival after 72 h in C. putoria and C. albiceps. The survival of parasitoids inside blowfly pupae that were submerged during their larval stage (3 days/age) decreased with the increase of submergence time. After the parasitoids reached the pre-pupal life stage, the survival was higher for all underwater periods. These observations can be useful in investigations of the decomposition of partially submerged bodies, or in cases of pupae found adhering to decaying flesh, hair, or clothes of corpses that were submerged after the larvae had developed and pupated.     

根据绿蝇属昆虫推断死亡时间的法医学研究进展

尸源性昆虫在某些刑事案件的侦破中占有重要地位,对于推断死者的死亡时间和推断尸体是否有转移有重要的作用。双翅目中的丽蝇科绿蝇属昆虫是尸体上常见的昆虫之一,通常最先到达尸体,而且最喜阳光,该特点以及在尸体上发现的绿蝇属昆虫幼虫的生长发育阶段,可以为刑事案件的侦破提供十分有力的证据。本文主要从生物形态学和分子生物学对绿蝇的种属鉴定以及绿蝇日龄的推断等方面,综述了根据绿蝇属昆虫推断死亡时间的法医学应用研究进展。     

Multiple-probe thermography for estimating the postmortem interval: I. Continuous monitoring and data analysis of brain, liver, rectal and environmental temperatures in 117 forensic cases

One hundred seventeen forensic postmortem cases have been studied under controlled conditions. In each case, temperatures of the brain, liver, rectum, and the environment were monitored over a period beginning shortly after death and ending up to 60 h postmortem. The four temperature measurements were recorded every 5 to 10 min using the Microwave Thermography System. Rectal and environmental temperatures were measured by electrical thermocouples while brain and liver temperatures were measured using microwave probes. Data acquisition, analogue-to-digital conversion (ADC), and data processing were provided by a microcomputer. The ADC technique is described and its problems are discussed. The data were then transferred to a mainframe computer for extensive curve-fitting and statistical analysis. The microcomputer-based ADC and data logging and acquisition were found to be accurate, fast, easy to implement, and useful for the field. The postmortem rate of human body cooling was found to be adequately represented by triple-exponential equations.     

A preliminary study of forensic entomology in Medellín, Colombia.

This is the first report of an ongoing study of insect succession on carrion carried out in Medellín, Colombia, using pigs (Sus scrofa) as a model to determine the insect sequence over 207 days. During this period, 2314 insects belonging to the following orders and families were collected: Diptera: Calliphoridae, Muscidae, Piophilidae, Sarcophagidae, Syrphidae, Otitidae; Hymenoptera: Apidae, Formicidae, Halictidae, Mutilidae, Vespidae; Coleoptera: Staphylinidae, Histeridae, Carabidae, Scarabaeidae, Silphidae, Dermestidae, Cleridae, Nitidulidae; Dermaptera: Forficulidae; Hemyptera: Gelastocoridae, Coreidae; Lepidoptera: Hesperiidae.Five decomposition stages were observed (fresh, bloated, active decay, advanced decay, and dry remains) and four insect ecological categories (necrophagous, predators, omnivorous, and incidental). During the fresh stage, the first insects that appeared were flies of the families Sarcophagidae and Muscidae and specimens of Formicidae (Hymenoptera). During the bloated period, species of Calliphoridae (Diptera) were predominant and the first to oviposit. During the third and fourth stages (active decay and advanced decay), the most abundant families were Calliphoridae and Muscidae, although Staphilinidae (Coleoptera) also stood out. During the last stage (dry remains), the dominant family was Formicidae (Hymenoptera) followed by Dermestidae (Coleoptera) with a large number of immature insects.     

A forensic entomology case from the Amazon rain forest of Brazil

The first case of application of forensic entomology in the Brazilian Amazonia is described. The corpses of 26 men were found in the rainforest in Rondonia State, Brazil. Fly larvae collected on the bodies during autopsy were identified as Paralucilia fulvinota (Diptera, Calliphoridae). No data or specimens were collected at the crime scene. At the laboratory, the larvae developed into pupae in 58 h and into adults in 110.5 h. The total development time for P. fulvinota was measured in field experiments inside the forest. The age of the larvae when collected from the bodies was estimated as the difference between the time required for them to become adults and the total development time for this species. The estimated age of the maggots and the minimum postmortem interval was 5.7 days.     

A comparison of statistical models for the analysis of complex forensic DNA profiles

Complex mixtures and LtDNA profiles are difficult to interpret. As yet there is no consensus within the forensic biology community as to how these profiles should be interpreted. This paper is a review of some of the current interpretation models, highlighting their weaknesses and strengths. It also discusses what a forensic biologist requires in an interpretation model and if this can be realistically executed under current justice systems.     

A statistical approach to aid examiners in the forensic analysis of handwriting

We develop a statistical approach to model handwriting that accommodates all styles of writing (cursive, print, connected print). The goal is to compute a posterior probability of writership of a questioned document given a closed set of candidate writers. Such probabilistic statements can support examiner conclusions and enable a quantitative forensic evaluation of handwritten documents. Writing is treated as a sequence of disjoint graphical structures, which are extracted using an automated and open-source process. The graphs are grouped based on the similarity of their shapes through a K-means clustering template. A person's writing pattern can be characterized by the rate at which graphs are emitted to each cluster. The cluster memberships serve as data for a Bayesian hierarchical model with a mixture component. The rate of mixing between two parameters in the hierarchy indicates writing style.     

家蝇幼虫发育形态学用于死亡时间推断的基础研究

对死亡现场出现较多的尸食性昆虫的幼虫在各个恒温下的形态变化进行观察 ,旨在筛选出某些可用于判断幼虫生长时间的形态特征 ,并根据这些特征将幼虫期各生长阶段加以详细地划分 ,以满足实际工作中较精确地推断幼虫年龄和死后间隔时间的需求。本文就其家蝇部分报道如下。1　材料与方法1 1　供试蝇种类家蝇 (Ｍｕｓｃａｄｏｍｅｓｔｉｃａ)由公安人员在死亡现场采集 ,带回实验室连续饲养 ,供实验用。1 2　方法1 2 1　样品收集　将家蝇所产新鲜卵接于猪肝上 ,猪肝放于盛有湿沙土的养虫笼中 ,用尼龙纱网扎紧 ,放进生化培养箱中培养 ,温度分别控…     

DNA typing for identification of some species of Calliphoridae. An interest in forensic entomology.

To determine precisely post mortem interval, larvae and puparium species found on a corpse have to be identified. Among more than 200 cases examined at the entomology department of the Institut de Recherche Criminelle de la Gendarmerie Nationale, two-thirds concerned corpses less than one month old. Therefore, insects from first and second screwworms are the most frequently found [1]. Some species commonly found in France, such as different Lucilia and Calliphora vicina Robineau-Desvoidy, are easily identifiable at an adult stage, but are almost impossible to differentiate at immature stages when only fragments of puparium or necrosed first instar larvae are available. For this reason, an easy and objective method of identification was thus searched by genetic analysis of these insects. Sequencing of partial gene of sub unit I of cytochrome oxydase has been used to predict restriction sites. Restriction enzyme cleavage of PCR products with Dde I allowed us to differentiate these species.     

An alternative for the extraction and storage of DNA from insects in forensic entomology

An important area of recent research in forensic entomology has been the use of insect DNA to provide identification of insects for fast and accurate estimation of time since death. This requires DNA to be extracted efficiently and in a state suitable for use in molecular procedures, and then stored on a long-term basis. In this study, Whatman FTA cards were tested for use with the Calliphoridae (Diptera). In particular, testing examined their ability to effectively extract DNA from specimens, and store and provide DNA template in a suitable condition for amplification using the polymerase chain reaction (PCR). The cards provided DNA that was able to be amplified from a variety of life stages, and thus appears to be of sufficient quality and quantity for use in subsequent procedures. FTA cards therefore appear suitable for use with calliphorids, and provide a new method of extraction that is simple and efficient and allows for storage and transportation without refrigeration, consequently simplifying the handling of DNA in forensic entomological cases.