 |
|
A glass fragment, a fiber
and an automotive paint chip, placed on
the surface of a penny to demonstrate the
typical size of trace evidence the microanalyst
is asked to examine
|
|
"Wherever he steps, whatever he touches, whatever he
leaves, even unconsciously, will serve as silent witness
against him. Not only his fingerprints or his
footprints, but his hair, the fibers from his clothes,
the glass he breaks, the tool marks he leaves, the paint
he scratches, the blood or semen he deposits or collects
- All of these and more bear mute witnessagainst
him. This is evidence that does not forget. It is not
confused by the excitement of the moment. It is not absent
because human witnesses are. It cannot perjure itself;
it cannot be wholly absent. Only its interpretation can
err. Only human failure to find it, study and understand
it, can diminish its value." (Crime Investigation ,
Kirk, Paul. L, New York : Interscience Publishers, 1953.)
The term "trace evidence" is generally thought of as
any type of evidence occurring in sizes so small that
it can be transferred or exchanged between two surfaces
without being noticed. The first scientist to formally
articulate a philosophical foundation for transfer-evidence
occurrence was the Frenchman, Edmond Locard (1877-1966):
The dust and debris that cover our clothing and bodies
are the mute witnesses, sure and faithful, of all our
movements and all our encounters.
 His
postulate that objects or surfaces which come into contact
always exchange trace evidence is known today as "the
Locard exchange principle." Today the forensic community
uses the term "trace evidence" to include associative-type
evidence that is usually microscopic in nature. This
evidence is used to show or substantiate contact between
people, a person and an object, or between two objects
(or places). The most common examples of this type of
evidence are: fibers
and textiles; paints
and coatings; plastics
and polymers; glass
and hair. In addition
to these services, the DOFS Headquarters Trace Evidence
Section offers the examination of fractured
materials, impressions
(footwear and tire) and general
materials.
One recommended method for packaging trace evidence
is a pharmaceutical paper
fold . The paper fold should then be sealed in an
outer container such as a paper bag or envelope for
submission to the laboratory.
|
