David V. Beresford

The effect of soil texture on the degradation of textiles associated with buried bodies

There are many factors which affect the rate of decomposition in a grave site including; the depth of burial, climatic conditions, physical conditions of the soil (e.g. texture, pH, moisture), and method of burial (e.g. clothing, wrappings). Clothing is often studied as a factor that can slow the rate of soft tissue decomposition. In contrast, the effect of soft tissue decomposition on the rate of textile degradation is usually reported as anecdotal evidence rather than being studied under controlled conditions. The majority of studies in this area have focused on the degradation of textiles buried directly in soil. The purpose of this study was to investigate the effect of soil texture on the degradation and/or preservation of textile materials associated with buried bodies. The study involved the burial of clothed domestic pig carcasses and control clothing in contrasting soil textures (silty clay loam, fine sand and fine sandy loam) at three field sites in southern Ontario, Canada. Graves were exhumed after 2, 12 and 14 months burial to observe the degree of degradation for both natural and synthetic textiles. Recovered textile samples were chemically analyzed using infrared (IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) to investigate the lipid decomposition by-products retained in the textiles. The findings of this study demonstrate that natural textile in contact with a buried decomposing body will be preserved for longer periods of time when compared to the same textile buried directly in soil and not in contact with a body. The soil texture did not visually impact the degree of degradation or preservation. Furthermore, the natural-synthetic textile blend was resistant to degradation, regardless of soil texture, contact with the body or time since deposition. Chemical analysis of the textiles using GC-MS correctly identified a lipid degradation profile consistent with the degree of soft tissue decomposition. Such information may be important for estimating time since deposition in instances where only grave goods and associated materials are recovered from a burial site.

Characterization of microsatellite loci in Phormia regina towards expanding molecular applications in forensic entomology

Forensic entomology involves the use of insects and arthropods to assist a spectrum of medico-criminal investigations that range from identifying cases of abuse, corpse movements, and most commonly, post mortem interval estimates. Many of these applications focus on the use of blowflies given their predicable life history characteristics in their larval stages. Molecular tools have become increasingly important in the unambiguous identification of larval blowfly species, however, these same tools have the potential to broaden the array of molecular applications in forensic entomology to include individual identifications and population assignments. Herein, we establish a microsatellite profiling system for the blowfly, Phormiaregina (Diptera: Calliphoridae). The goal being to create a system to identify the population genetic structure of this species and subsequently establish if these data are amenable to identifying corpse movements based on the geographic distribution of specific genetic clusters of blowflies. Using next generation sequencing technology, we screened a partial genomic DNA sequence library of P.regina, searching for di-, tetra-, and penta-nucleotide microsatellite loci. We identified and developed primers for 84 highly repetitive segments of DNA, of which 14 revealed consistent genotypes and reasonable levels of genetic variation (4-26 alleles/locus; heterozygosity ranged from 0.385 to 0.909). This study provides the first step in assessing the utility of microsatellite markers to track the movements and sources of corpses via blowflies.

SAMPLING ADULT BLOW FLIES (Diptera: Calliphoridae) AT PIG CARCASSES WITH STICKY TRAPS: EFFECTS OF TRAP COLOUR, HEIGHT, AND INCLINATION

ABSTRACT Blow fly species (Calliphoridae) are commonly used in forensic investigations. Adults are often sampled at crime scenes and during species surveys using sticky traps. Trap catches are species specific and can vary due to trap design. We tested sticky traps set near a fresh pig carcass to identify catch differences of blow fly species based on trap colour (black, white, yellow, green, blue, and red), trap height (31, 61, 91 cm), and trap angle (horizontal, 45°, vertical). Phormia regina were most abundant on white traps placed low and slanted. Lucilia sericata catches were largely on yellow traps, but unaffected by trap angle or height. Calliphora vicina and Lucilia illustris catches were similar across all traps, although Calliphora vicina tended to be caught more often on blue vertical traps. In general, vertical or slanted traps at low and middle height caught the most forensically relevant species. From these results, two types of sticky traps should be used at crime scenes or for species surveys: white, slanted traps set at 31 to 51 cm high targeting Lucilia species and P. regina; and vertical blue or black traps 60 cm high to target Calliphora species, such as C. vicina.

Postfeeding larval dispersal behavior of late season blow flies (calliphoridae) in Southern Ontario, Canada.

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

Ground penetrating radar use in three contrasting soil textures in southern Ontario

Abstract Ground penetrating radar (GPR) is a non-invasive, geophysical tool that can be used for the identification of clandestine graves. GPR operates by detecting density differences in soil by the transmission of high frequency electromagnetic waves from an antenna. Domestic pig (Sus scrofa domesticus) carcasses were clothed in 100% cotton t-shirts and 50% cotton/50% polyester briefs, and buried at a consistent depth at three field sites of contrasting soil texture (silty clay loam, fine sand and fine sandy loam) in southern Ontario. GPR was used to detect and monitor the graves for a period of 14 months post-burial. Analysis of collected data revealed that GPR had applicability in the identification of clandestine graves in silty clay loam and fine sandy loam soils, but was not suitable for detection in the fine sandy soil studied. The results of this research have applicability within forensic investigations involving decomposing remains by aiding in the location of clandestine graves in loam soils in southern Ontario through the use of GPR.

Using Frons Width to Differentiate Blow Fly Species (Diptera: Calliphoridae) Phormia regina (Meigen) and Protophormia terraenovae (Robineau-Desvoidy)†

Protophormia terraenovae (Robineau‐Desvoidy) (Diptera: Calliphoridae) and Phormia regina (Meigen) (Diptera: Calliphoridae) are morphologically similar blow fly species commonly used for estimating postmortem intervals. Field collection and storage of adults can result in color changes, in particular on calypters and palps; often collected specimens show damage such as wing fray or fungal growth. We measured the frons width: total head width ratio using photographs (ImageJ version 1.49) to differentiate these two species. Both sexes were distinguishable to species, with the greatest difference between males: 12.34% P. terraenovae versus 1.62% P. regina, less so for females: 40.25% P. terraenovae, versus 33.65% P. regina. Incorporating this feature into future blow fly keys would help with distinguishing field‐caught specimens when other features are obstructed.