An investigation into the recovery of ignitable liquid residues from entomological samples using solid-phase microextraction
- Publication Type:
- Thesis
- Issue Date:
- 2011
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The analysis of fire debris can indicate the presence of an ignitable liquid, but the
volatility of these substances means that the likelihood of detecting them diminishes
over time. It is proposed in this thesis that when a scene contains burnt human
remains, entomological samples can be analysed for the detection of ignitable liquids,
as an alternative to fire debris. It is hypothesised that a larva’s ability to invade areas
protected from the external environment, such as the natural body openings of
cadavers, and accumulate substances present in the tissue in which they are feeding,
will extend the period in which ignitable liquids can be detected.
In small-scale experiments conducted under controlled laboratory conditions, petrol
and kerosene were detected in larvae of the blow fly Lucilia cuprina, (Wiedemann)
(Diptera: Calliphoridae) that had been fed on meat burnt using these ignitable liquids.
Four sample sets of meat, each with six replicates (24 meat samples in total) were
prepared. The first and second sets were burnt using petrol and kerosene,
respectively. The final two sets were control groups. Six larvae were collected daily
from each of the 24 meat samples for a period of five days. Once the adults had
emerged, six adults and six puparia were also collected from each meat sample. All of
the entomological samples collected were analysed using solid-phase microextraction
gas chromatography-mass spectrometry (SPME-GC-MS). It was found that larvae of
the blow fly Lucilia cuprina can be used in a small-scale setting to detect both petrol
and kerosene from burnt substrates for at least five days. Positive results for the
ignitable liquids of interest were also obtained for a limited number of adult flies and
puparia.
Given these findings, further research was conducted using a more realistic
experiment (conducted in duplicate) that mirrored a casework scenario more closely.
Sample sets identical to those in the small-scale experiments were prepared using 24
piglets, each approximately 1.39 kg in weight, instead of the meat samples. These
piglets were placed a minimum of 51 m apart at the Holsworthy Military Area in New
South Wales, Australia, for three days. After this time, the piglets were transferred to
a controlled laboratory. It was found during these fieldwork experiments that petrol
and kerosene could be successfully detected in larvae for as long as eight days, and in
the adult and puparia samples for at least one month. These findings confirm the
significant advantage of using entomological samples as an alternative to fire debris, in
that they extend the period available for sampling volatile ignitable liquids by at least
one month. In particular, puparia can withstand changing climatic conditions, and
unlike the larvae and adults, are immobile and hence could be found close to human
remains even after considerable time has elapsed.
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