Abstract
Insects found at a crime scene can produce traces referred to as fly artifacts (FA) due to their movement over the corpse and the manner in which they feed upon it. These can be detrimental for carrying out criminal investigations. Confusing a FA with a genuine bloodspot can lead to misinterpretations, also taking into consideration that FA may contain a human DNA profile. The aim of the present study was to employ scanning electron microscopy (SEM) for the analysis of FA produced by Calliphora vomitoria on hard surfaces and fabrics that are commonly present at crime scenes. FA and control bloodstains were produced under experimental conditions on metal, glass, plaster, cotton, and polyester. After macroscopic analysis, FA were examined at standard low (20–40 ×), medium low (300–600 ×), and high ultrastructural (1200 ×) magnification through a SEM Stereoscan 360, Leica, Cambridge. SEM analysis enabled the identification of distinctive features of FA on hard surfaces, namely, amorphous crystals, micro-crystals with a morphology similar to those of uric or micro-crystals with a comparable morphology to cholesterol, absent in controls. Moreover, red blood cells (RBC) were absent in FA but were always present in controls. On cotton, for both FA and controls, the drop was almost completely absorbed and thus indistinguishable from the underlying fabric texture. On polyester, FA showed amorphous/crystal-like deposits and no RBC, as observed on hard surfaces, except for those showing a completely flat surface. SEM analysis appeared to be suitable for differential diagnosis between FA and genuine bloodstains on hard surfaces, although the results may be inconclusive on tested fabrics.
Highlights
Insects found at a crime scene can be of use to many types of forensic investigation
The aim of the present study was to employ scanning electron microscopy (SEM) for the analysis of fly artifacts (FA) produced by Calliphora vomitoria (C. vomitoria), on five different surfaces that can be commonly present in a crime scene, namely, metal, plaster, glass, cotton, and polyester, in order to obtain further information on the ultrastructural distinction between FA and genuine bloodstains
FA on hard surfaces were divided into dark color FA (DFA), light color FA (LFA) and tailed FA (TFA)
Summary
Insects found at a crime scene can be of use to many types of forensic investigation. They can provide information about time since death, season of death, the primary crime scene, movement or concealment of the remains following. The presence of insects does not always aid investigations and may even prove counterproductive by reason of their movement over the corpse and the manner in which they feed on it. Foraging activity is known to cause the most problematic alteration of the death scene, as insects can create unique stains or intermix fly artifacts with bloodstains and other human body fluids as a result of their digestive process [4]. Confusing FA with genuine bloodspots can lead to misinterpretations, considering that FA may contain human DNA profile [6]
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