Note: There are many elements at the
crime scene that fall under the term trace evidence, which can overlap with
the pages listed above. I will attempt to create pages for each of the
elements listed below in the near future.
Before beginning there are a few concepts that need to be
explained that will be used within the following text.
Locard's Exchange Principle - Basically, this
principle states that everything leaves a trace when two objects come into
contact with one another. At a crime scene an offender and victim will
bring something to the scene and also leave something behind. This may
be a hair, fiber, fluid or dirt, but something is left behind.
Class Characteristics - This indicates evidence which
identifies an item or sample that is of similar type or having similar
characteristics to a sample taken from the scene of a crime. Examples
of evidence having class characteristics are shoes, tires, and tools.
Individual Characteristics - This indicates evidence
which identifies an item or sample that is unique to a sample taken from the
scene of a crime. DNA and fingerprints have individual characteristics
because they are able to positively identify a source as compared to the
sample. However, the previously mentioned evidence that was identified
having class characteristics can also have individual characteristics as
well. For example, a shoe, tool, or tire may have unique wear or
defects that can only be explained as coming from the evidence in question.
Below is a listing of possible trace evidence that can be of
importance during an investigation.
Hair & Fiber
Hairs and fibers can
be of great importance in an investigation. Hair and fiber evidence
was presented at the trial of Wayne Williams to assist in linking him to
many murders and ultimately convicting him of at least two of the crimes.
Hair and fiber allow investigators to place a suspect at the scene of the
crime or as in the case of Williams, place the victim in contact with the
suspect. Hair can have class characteristics or individual
characteristics if there is DNA available, while fiber is mainly class
This section will be covered in more
detail under the pathology section.
Paint can be used to place a suspect
at the scene of a crime in several ways. Paint can be chipped from a
car in an accident leaving a sample to be compared to a suspect's car during
an investigation, or there have also been cases where an offender works as a
painter and leave paint chips on a victim. In other cases offenders
have damaged their car at the scene of a crime and paint from another object
was transferred onto their car.
Fluids can consist of semen, saliva or
sweat that can assist in identifying an offender in an investigation.
Glass fragments can be compared to
place a suspect at the scene of a crime by testing the density of each to
determine if they came from the same source. Glass also breaks or
cracks in a consistent manner that can assist investigators in
reconstructing what occurred during the commission of a crime.
Soil & Dust
Soil and dust evidence can provide an
indication that an offender was at the scene of a crime and can also suggest
possible areas where the offender lives or works.
Shoe Impressions (see Impression Evidence)
Blood (see Blood Spatter & DNA Evidence)
Bite Marks (see Odontology)
Tool Marks (see Impression Evidence)
Questioned Documents (use link above to view)