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| The motto
'every contact leaves a trace' by Edmond Locard, a well
known criminologist, still guides today's investigation
in that a criminal cannot prevent leaving traces of
themselves at a crime scene and always take with them
some evidence that they were present at the crime scene.
It is this theory that has helped to solve many crimes. |
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Select one of the following topics
to read more:
--> Trace
evidence
--> Collection
--> Where
to search
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| Trace
Evidence |
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| Finding
the traces of evidence that could link a suspect to
a crime scene is difficult, as these are usually very
vague and is easily destroyed or lost.The term trace
evidence is used to describe these small samples and
covers such artifacts as hair, paint flecks, soil, fibres,
dust and tiny pieces of glass, which can all be used
to track down a criminal. |
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The most basic examination on any piece of evidence
is underneath the microscope. Photo courtesy of Californian
Association of Criminalists. |
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| Collection |
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| The collection of the
trace evidence requires just as much technique, time
and patience as finding normal evidence. Larger pieces
of trace evidence can be retrieved using a magnifying
lens and a pair of tweezers. Forensic vacuums, involving
a piece of filter paper over the suction, suck small
material onto the paper for analysis in the laboratory.
Tape lifts are also effective for removing evidence
from smaller areas and investigators remove portable
objects using bags so that the smaller particles can
be removed later on in the lab. Washing and scraping
these portable objects in the lab reveals trace particles
that would have otherwise escaped unnoticed. |
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| Where
To Search |
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Clothes
that a criminal wore at the crime scene collect
dirt and other artifacts, which fall off in a
matter of hours and brushing can remove what hasn't
already fallen off, thus making such evidence
relatively useless. There is however, the exception
that the clothing contains pouch like spots, which
would likely hold trace evidence. The evidence
is usually so small it is not normally visible
to the naked eye, so investigators are faced with
the problem of needing to find something they
can't see. This problem is overcome by performing
a thorough search of the crime scene and making
guesses from the search as to what they should
look for and where they might find this. For example,
on a couch, seams on the cushions, underneath
the cushion and on the arms of the chair can often
contain fibres from the suspect or victim that
can incriminate a person, when at a first glance,
the object appears to contain no evidence. |
| *Rolled
up sleevs, pockets and other miscellaneous slots
are appropraite places to search for trace evidence.
Photo courtesy of www.morguefile.com.
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