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B.
The Crime, the Crime Event, and the Crime Scene
A 
 
crime
is a violation of a statutory law. Therefore, a 
 
crime scene
might be
defined as any location or item connected with the crime. We distinguish
this from the 
 
crime event
which is the actual commission of the crime.
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Recognition of Physical Evidence
103
Recognition of evidence may occur at any time after the crime occurs.
However, the interval between the crime event and securing the scene, and
any further time that passes before evidence is detected, affects our ability
both to recognize evidence as such and to relate it to the crime event. The
simple passing of time obscures our ability to determine by whom, or in
connection with what, the material was deposited in some particular location.
The possibility of connecting multiple scenes also declines with time.
Additionally, the evidence item acquires a history between the crime
event and the recognition of it as evidence. It is precisely during this time
period that the sample is subjected to unknown and unknowable factors,
creating an unbreachable void in our understanding of evidence. It defines
the uncontrolled nature of case samples.
 
C.
What Is Evidence?
Interestingly, in the United States, at least, the law defines evidence only by
its relevance. Relevant evidence is admissible; irrelevant evidence is inadmis-
sible. The following are excerpts from Article I and Article IV of the U.S.
Federal Rules of Evidence*
 
 
(1999) (Figure 5.2).
Thus, it is left to science to define the conceptual nature of 
 
physical
evidence
. The material attributes of physical evidence require simply that it
be detectable. This may be accomplished by human senses or enhanced by
optical, physical, or chemical means. Physical evidence may be examined,
compared, or analyzed by those same means. Conceptually, evidence must
be associated with a crime. As interesting as it may be to examine your office
conference room for fingerprints or test unknown stains in the parking lot
for blood, these samples would not become evidence unless someone stole
the boss’s favorite coffee mug or a murder was committed outside the build-
ing. Incorporating the legal requirement, evidence must therefore provide
factual information about the crime, establishing its relevance to a criminal
proceeding.
Let’s take a simple example. A man walking through a park is assaulted, and
a fist fight ensues. The assailant bloodies the nose of the victim. The victim
reports the assault to the police, who eventually apprehend a suspect. The
clothing of both are collected, and the police enlist the aid of the scientist
to determine whether the suspect is in fact the assailant. The testimony of
the victim, the testimony of the suspect, any eyewitness accounts, and the
clothing collected from both persons involved might all be considered relevant
* The Uniform Rules of Evidence (1988) are very similar to the Federal Rules of Evidence.
They have begun to be adopted by states to accomplish a goal of standardization.
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Principles and Practice of Criminalistics