Bayesian networks for evaluation of evidence from forensic entomology.

In the aftermath of a CBRN incident, there is an urgent need to reconstruct events in order to bring the perpetrators to court and to take preventive actions for the future. The challenge is to discriminate, based on available information, between alternative scenarios. Forensic interpretation is used to evaluate to what extent results from the forensic investigation favor the prosecutors' or the defendants' arguments, using the framework of Bayesian hypothesis testing. Recently, several new scientific disciplines have been used in a forensic context. In the AniBioThreat project, the framework was applied to veterinary forensic pathology, tracing of pathogenic microorganisms, and forensic entomology. Forensic entomology is an important tool for estimating the postmortem interval in, for example, homicide investigations as a complement to more traditional methods. In this article we demonstrate the applicability of the Bayesian framework for evaluating entomological evidence in a forensic investigation through the analysis of a hypothetical scenario involving suspect movement of carcasses from a clandestine laboratory. Probabilities of different findings under the alternative hypotheses were estimated using a combination of statistical analysis of data, expert knowledge, and simulation, and entomological findings are used to update the beliefs about the prosecutors' and defendants' hypotheses and to calculate the value of evidence. The Bayesian framework proved useful for evaluating complex hypotheses using findings from several insect species, accounting for uncertainty about development rate, temperature, and precolonization. The applicability of the forensic statistic approach to evaluating forensic results from a CBRN incident is discussed.

Strengthen forensic entomology in court--the need for data exploration and the validation of a generalised additive mixed model.

Developmental data of juvenile blow flies (Diptera: Calliphoridae) are typically used to calculate the age of immature stages found on or around a corpse and thus to estimate a minimum post-mortem interval (PMI(min)). However, many of those data sets don't take into account that immature blow flies grow in a non-linear fashion. Linear models do not supply a sufficient reliability on age estimates and may even lead to an erroneous determination of the PMI(min). According to the Daubert standard and the need for improvements in forensic science, new statistic tools like smoothing methods and mixed models allow the modelling of non-linear relationships and expand the field of statistical analyses. The present study introduces into the background and application of these statistical techniques by analysing a model which describes the development of the forensically important blow fly Calliphora vicina at different temperatures. The comparison of three statistical methods (linear regression, generalised additive modelling and generalised additive mixed modelling) clearly demonstrates that only the latter provided regression parameters that reflect the data adequately. We focus explicitly on both the exploration of the data--to assure their quality and to show the importance of checking it carefully prior to conducting the statistical tests--and the validation of the resulting models. Hence, we present a common method for evaluating and testing forensic entomological data sets by using for the first time generalised additive mixed models.

"The horizon opened up very greatly": Leland O. Howard and the transition to chemical insecticides in the United States, 1894-1927.

The transition to synthetic chemicals as a popular method of insect control in the United States was one of the most critical developments in the history of American agriculture. Historians of agriculture have effectively identified the rise and charted the dominance of early chemical insecticides as they came to define commercial agriculture between the emergence of Paris green in the 1870s and the popularity of DDT in the 1940s and beyond. Less understood, however, are the underlying mechanics of this transition. this article thus takes up the basic question of how farmers and entomologists who were once dedicated to an impressively wide range of insect control options ultimately settled on the promise of a chemically driven approach to managing destructive insects. Central to this investigation is an emphasis on the bureaucratic maneuverings of Leland O. Howard, who headed the Bureau of Entomology from 1894 to 1927. Like most entomologists of his era, Howard was theoretically interested in pursuing a wide variety of control methods--biological, chemical, and cultural included. In the end, however, he employed several tactics to streamline the government's efforts to almost exclusively support arsenic and lead-based chemical insecticides as the most commercially viable form of insect control. While Howard in no way "caused" the national turn to chemicals, this article charts the pivotal role he played in fostering that outcome.

[Dumping of corpses in compost bins--two forensic entomological case reports]. / Leichen-"Entsorgung" in einer Biotonne--zwei forensisch-entomologische Fallberichte.

Two cases from the Ruhr Area in Western Germany are presented. In each case, the deceased had been wrapped in plastic bags and placed inside a large compost bin in the backyard of the property. In both cases, the relatives claimed that the decedent had died from a natural cause and that they had concealed the body to ensure the further payment of the nursing care and pension benefits. In the first case, the responsible person stated that the body had been inside the bin for three years; in case 2 the postmortem interval indicated was 6 months. In spite of the closed lid of the bin the insect infestation was extensive and rich in species: Empty pupal cases of several blowfly species were collected as well as histerids and pupal cases of Fannia scalaris in the first case. In case 2, phorids and larval skins of dermestids were also found.

[Forensic entomology exemplified by a homicide. A combined stain and postmortem time analysis]. / Forensische Entomologie am Beispiel eines Tötungsdeliktes. Eine kombinierte Spuren- und Liegezeitanalyse.

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.

Postmortem insect activity may mimic perimortem sexual assault clothing patterns.

Determination of perimortem sexual assault can be confounded in homicide cases in which only badly decomposed or skeletal remains are recovered. One indicator of assault is a characteristic pattern of clothing disarray, including tearing, removal, or displacement of clothing. Preliminary findings from two studies of clothed pig carrion of approximate human size (59 to 162 kg) reveal that postmortem insect activity, particularly maggot masses, and natural decompositional changes such as bloating can produce changes to clothing which mirror those seen in cases of sexual assault.