Textile fibres as a form of trace evidence are rarely used. This is mainly due to the
expense of analysis and the lack of forensic fibres databases. The need for the
generation of textile fibre data collections to aid interpretation has been expressed
frequently. This study investigated whether inexperienced personnel, such as
undergraduate and postgraduate students, could provide data that was appropriate for
a forensic fibres database after only a small amount of training.
To facilitate this investigation, a proficiency testing scheme was designed and
implemented to assess the ability of participants, participating in higher education, to
analyse synthetic fibres using polarized light microscopy; a technique regularly used
in casework by forensic practitioners. Six synthetic fibres (labelled F to K) that
would commonly be found in the environment were analysed by the participants in
terms of their width, birefringence, sign of elongation, cross-sectional shape and
delusterant identification. Each of the six test samples were given an assigned value
which was generated by using the consensus values generated by experts, for the
qualitative parameters or the mean value (x**) of the student participants results after
erroneous data points were removed, for the quantitative parameters. The standard
deviation (s**) was also calculated for each quantitative parameter after the identified
errors were removed. The results of the proficiency testing scheme were explored
primarily by directly comparing the participants’ results to the assigned values or by
the use of z scores, which enabled a pass, alert or fail to be given to each of the
quantitative results. A Synthetic Fibres Database (SFD) was created to organise, store
and allow interrogation of the proficiency test results.
Overall, 460 participants from national universities undertook the proficiency testing
scheme, 391 of which were undergraduate students and 69 of which were
postgraduate students. It was found that the majority of both the undergraduate and
postgraduate students were competent at analysing the qualitative parameters with
81.8%, 87.7% and 88.7% of undergraduates and 89.9%, 88.4% and 92.8% of
postgraduates correctly analysing 4 or more fibres for sign of elongation, delusterant
and cross-sectional shape respectively. It could be seen that both the undergraduate
and postgraduate participants found the quantitative parameters more difficult than the
qualitative with birefringence measurements being identified as the parameter which
participants found the most difficult to produce accurate answers in. For the width
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results, an average of 56.3% of undergraduates and 65.2% of postgraduates obtained a
pass rating for each of the individual test samples. For the birefringence
measurements, an average of 49.5% and 64.1% of undergraduate and postgraduate
participants respectively, obtained a pass. It was found that although both the
undergraduate and postgraduate students produced results which showed fairly high
accuracy for the individual fibres, the performance over all 6 fibres was lower with
fewer passes or alerts being attained for all 6 test fibres for both width and
birefringence measurements.
When comparing the undergraduate and the postgraduate performances it was found
that generally overall the postgraduates performed better with a higher proportion of
postgraduate participants passing the individual parameters and a higher proportion of
postgraduate results to undergraduate results obtaining a pass or alert status for each
fibre for both the width and birefringence measurements.
Full error analysis was conducted upon the participants’ data. It was found that
participants were subject to errors which fibres experts would be less likely to make,
for example, calculation errors.
The effect of any variation within and between test samples was explored and it was
found that limited variation in the qualitative parameters was present but some test
slides exhibited variation in width along the length of the fibre and between test
slides. The effect of using different microscope types and accessories was found to
have a small affect on the measurement of birefringence only.
Ultimately, this research project has shown that although skill is required, it would be
possible to produce a database that is fit for purpose by utilising chosen data
generated by inexperienced personnel.
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