8127/frame/fm

 
c.
The Dynamic Crime Scene
A crime scene is a dynamic environment. The evidence begins to change
literally the instant after the action has taken place.* The longer it has been
since the crime was committed, the less the scene will resemble the original.
Often, one of the largest holes in our understanding of a case is what hap-
pened between the commission of a crime and its recognition by responsible
personnel. A crime scene always exists in some form, but the more distant
in time from the 
 
crime event
, the less resemblance it may have to its state at
the moment the crime was committed.
There is nothing anyone can do to halt the continual changes to a scene,
but we can at least minimize the human contribution to that alteration. To
do that we must become part of the 
 
crime scene gestalt
. It is essential to
recognize that the moment you enter a scene, 
 
you
become a part of the scene.
To understand this, it’s useful to paraphrase the 
 
Heisenberg uncertainty prin-
ciple
** on a macrolevel; you change the scene simply by being in it. Further-
more, the very act of processing the scene will change it. You will walk around
the area, you will examine and record it in various ways, you will take things
from it by the very act of collecting evidence. The alterations you introduce
can either be minimal or egregious, deliberate or unconscious, depending
on how you proceed.
For example, let’s say a murder has taken place on a Friday evening in
an abandoned warehouse. Blood evidence is deposited on the floor of the
warehouse. However, gaping holes in the roof allow rain to enter later that
night. By Saturday morning, when the investigators have finally realized that
a murder has taken place, no 
 
obvious
blood evidence may remain. This is an
extreme, although not uncommon, example. Forces that may act to alter a
crime scene may be inanimate (e.g., the weather), living (e.g., microorgan-
isms or animals), or human (e.g., attempted cover-up). Although we cannot
know or control how the crime scene was altered before the arrival of inves-
tigating officers, we can act to minimize the inevitable disruption caused by
* The only unchanging element in a crime scene is the obligatory cold coffee and stale
doughnuts needed by the investigators to sustain them on the job, these days required to
be consumed outside of the secured area.
** The 
 
Uncertainty Principle
, published by Werner Heisenberg in 1927 states that, for
subatomic particles, “The more precisely the position is determined, the less precisely the
momentum is known in this instant, and vice versa. In other words, we can't simulta-
neously know the location and velocity of a quantum-scale particle, because the act of
measuring either disturbs the other. We take the liberty of stretching the concept to a
macro level to make the point that our very entrance into the crime scene disturbs it;
however, we can’t know what’s in it without being in it. 
8127/frame/ch08 Page 202 Friday, July 21, 2000 11:45 AM

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Good Field Practice — Processing a Crime Scene
203
our entrance into the scene. An example of how a crime scene was uninten-
tionally disrupted by assuming too small a scope is given in Sidebar 7.