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B.
The Nature of Matter
The examination of evidence relies on an understanding of the fundamental
nature of matter. When matter becomes evidence by virtue of its connection
with a criminal act, this modulates to an understanding of the 
 
nature of the
evidence
. Matter (and hence physical evidence) is the “stuff” around us that is
composed of the fundamental building blocks of the universe, ordered according
to well-articulated chemical and physical principles. We need not concern our-
selves with subatomic particles when discussing physical evidence, but rather
atoms and how they are arranged to compose our physical world. Because they
can only be arranged in specific ways allowed by the laws of chemistry and
physics, their fundamental properties remain constant and reproducible each
time we examine or analyze them. Forensic scientists take advantage of these
properties of matter in forensic science by applying tests designed to reveal the
underlying nature of the material so that we might draw some useful conclusions
about what it is, and what the potential source of the evidence might be.
A forensic scientist is thus well grounded in the fundamentals of chem-
istry and physics; here is the starting place for understanding what property
of an item of evidence might be examined to answer a useful legal question.
Analysts must come to appreciate how the material is generated, whether by
nature or by human hands; they must ascertain the characteristics that define
the material, including which of those characteristics are shared with other
materials, and which are unique to this material. From the synthesis of this
knowledge comes the ability to determine what traits may be used to cate-
gorize or classify the material, what properties might lead to source deter-
mination, and whether that source might be unique.
For bloodstain patterns and ballistics, an understanding of the substance,
combined with a grasp of its dynamic interaction with the environment, is
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The Origin of Evidence — Divisible Matter and Transfer
87
integral to interpreting the evidence. For this kind of “dynamic” evidence,
we are as interested in the process as the end result. In particular, we look to
this type of evidence to assist in the final reconstruction of the event, in other
words, the movement of matter through space and time. We will address this
aspect in more detail in Chapter 7.
Once an appreciation is gained for the fundamental nature of matter,
and consequently for physical evidence, it is necessary to describe those
principles and processes that form the unique aspects of the enterprise we
call forensic science.