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Evidence comes in many forms. It may be given orally or
in writing from an ordinary witness or an expert witness
or a police officer or other. It may be in the form of
physical objects obtained from a scene of crime or
suspect some of which are real exhibits in a case
brought before a court. It can be physical material
recovered in forensic examination or the adduced
findings of such an examination which can be used to
suggest the occurrence of a fact. There are many other
types of evidence which have particular meanings in law.
A list of these was provided in the first year course,
Introduction to the Principles of Forensic Science.
This course module addresses issues relating to evidence
which emerges as a result of forensic examination, of
scenes of crime and in the forensic or analytical
laboratory. It focuses on the interpretation of the
findings in the context of the case and the presentation
of these findings and expert opinion in the witness box.
For example, a sample of colourless liquid obtained from
the property of a suspect in a case of arson is found to
be white spirit by gas chromatography - mass
spectrometry. Examination of a sample of a solvent
residue obtained from the scene of a fire appears to
show a very different gc-ms profile. How can these
findings be interpreted, how do you arrive at an expert
opinion, how do you present this to the courts and how
do you defend your work under vigorous
cross-examination?
The scientific interpretation of evidence emerging from
an experiment to identify a substance might seem
straight forward, especially where sound scientific
principles underlie the methods employed in examination.
For example, either the substance is or is not white
spirit, or a specific amphetamine, or ammonium
perchlorate or a type of glass. The interpretation of
evidence can, however, be much more problematic where
the interpretation is more difficult to frame on sound
scientific principles. For example, is fingerprint or
document or hair or earmark or fire scene examination
based on sound scientific principles, and can any of
these evidence types really be used to identify or
implicate an individual? And how does natural variation
(statistical randomness) or alternative hypotheses
(statistical likelihood) affect any conclusions that can
be made? This module looks at these issues, it also
addresses the question of scientific method as opposed
to "junk science."
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Finally, some students have asked which of the
material provided below (and in lectures) is
"necessary." That's a loaded question! If you
want to have sufficient material at your
fingertips to be able to answer examination
questions then you must know and be able to use
the information given in the Lecture Overheads
and Notes marked with an asterisk (*),
which are deemed to be essential reading. I
would hope your interests and aspirations extend
beyond this immediate objective. It is for this
reason that additional Notes are provided. The
Notes contain all of the material in the Lecture
Overheads and a small amount of additional
reading material. Students who have read around
the subject, either through the Notes or through
the much wider literature typically provide more
comprehensive answers in assessment. The
consequences should be obvious, and the choice
is yours! |
Dr Steven
Dobrowski
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