8127/frame/fm

 
Figure 5.2
Ar
ticle I and Ar
ticle IV
.
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Recognition of Physical Evidence
105
evidence under the law. However, only the clothing comprises physical
evidence. It is tangible, so we can examine and analyze it; it is associated
with a crime by virtue of being worn by the victim or assailant; its relevance
can only be established after it is examined and analyzed. The simple fact
of its presence on the participants probably does not help to establish any
facts about the crime; the presence of bloodstains, fibers, or damage might.
 
1.
The Search for Evidence
Some types of evidence patently relate to the criminal event. Blood from a
stabbing, bullets from a deceased person, or broken glass from a burglary,
clearly derive from the crime incident and are readily discerned. The recog-
nition of such evidence is usually accomplished simply by looking. But for
other types of evidence, the connection to the crime is not necessarily obvi-
ous. We each lose hundreds of hairs a day (some of us more than others), so
the finding of human hair almost anywhere is predictable. The finding of
human hairs at a crime scene is therefore expected, whether or not the hairs
bear any relation to the crime. The presence of hairs that appear to have been
forcibly removed immediately suggests increased relevance to the crime;
bloody clumps of hair increase that relevance exponentially.
The case of 
 
People v. Axell
involved the stabbing murder of a convenience
store clerk by an unknown female. The victim was found clutching 10 anagen*
hairs in his fist, a circumstance consistent with the victim having pulled the
hair from someone’s head during a struggle. Because anagen hairs must be
forcibly removed from the scalp, it is reasonable to infer that a clump of
hair clutched in the hand of a murder victim is related to the assault that
killed him. DNA analysis of the hairs by RFLP** showed genetic concor-
dance between the evidence hairs and a reference sample from Linda Axell.
While the DNA analysis was vital to increasing the strength of the evidence
by virtually individualizing the hairs to Linda Axell, their significance in the
context of the crime was determined wholly by circumstance. The hairs
were determined to be relevant to the homicide by virtue of their location
(his hand) and by their apparent state as pulled hairs. If they weren’t, the
results of the DNA analysis would have been less significant in the context
of the crime (and probably impossible at the time!).***
Remember that the law asks the relevant question. Whether it is asked
by a detective, a criminalist, or an attorney, the elements of a crime must be
* Anagen hairs are in a growth phase and would not be expected to fall out easily.
** Restriction fragment length polymorphism, the first DNA technique to be widely used
and accepted.
*** RFLP analysis requires follicular material to be present on the hair root. Fallen telogen
hairs are usually not amenable to RFLP testing.
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106
Principles and Practice of Criminalistics
proved; this defines the purpose of the investigation and, by extension, the
examination of the crime scene. The legal question also impacts what will
ultimately be considered evidence. That we can ascertain all the evidence that
exists just by looking runs counter to the entire evolution of detective work.
Just looking does not work; 
 
looking with purpose
, or 
 
searching
, is central to
a competent investigation. To search effectively, the investigator must discern
what evidence might reasonably be relevant to the crime or he will waste
inordinate amounts of time searching aimlessly.
Whether we are aware of it or not, we constantly form provisional
hypotheses about life as well as about crimes. I assume that the train will
arrive at the station at exactly at 8:14 
A
.
M
. Therefore, if I get there at exactly
8:13, I will even have a chance to grab a cup coffee before boarding the train.
My hypothesis is based on the fact that the train always arrives on time or
late, and on my assumption that this pattern will continue today. Similarly,
I assume that I will find my keys hanging on the hook next to the door when
I go to leave the house. This is based on the fact that I usually place the keys
there upon entering, and the assumption that I did that last time I entered,
and that neither I nor anyone else has moved them in the meantime. Without
these provisional hypotheses, we would not be able to function in life; each
decision would require starting from neutral, with all possibilities equally
probable. We need not try to eliminate preconception, but to identify our
hypotheses and the assumptions on which they are based. We can then use
this information to guide our actions, and we can change our hypotheses
when new information is presented to us.
When presented with the aftermath of a criminal event, the goal of law
enforcement is to solve the crime and charge the guilty party in the most
efficient and expeditious way possible. Thus, the investigator in charge of the
scene must determine what crime has been committed, what are the legal
elements, and what evidence he expects to find. Immediately following rec-
ognition of the crime, the investigator will learn information that will lead to
a preliminary hypothesis. The challenge presented to an investigator is to
determine what evidence exists. At the same time, he must consider the ques-
tion of what evidence 
 
should
exist given that this crime occurred. These
complementary notions are based on the 
 
expectation
of the investigator (or
the criminalist, if given access to the scene). To harbor an expectation, we
require information about the crime. In other words, we must anticipate what
physical manifestations we expect as a consequence of that event.
For instance, the crime is murder, the 
 
modus operandi
is similar to a
string of other crimes, and it occurred at the known headquarters of a local
gang. It is not unusual to develop a prime suspect quite early in the investi-
gation based on information that has accumulated in police files. The inves-
tigator will then direct the search for evidence 
 
assuming that this crime was
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Recognition of Physical Evidence
107
 
committed by this person.
While a provisional hypothesis is necessary to
process a crime scene and begin the search for evidence, the investigator must
also be willing to update his hypothesis based on new information. At some
point, we become convinced that no piece of information will change our
hypothesis about what happened.
The scientist has tried to define her role apart from the law and usually
feels some obligation to maintain the same objectivity that characterizes her
other scientific work. This does not imply that she holds no preconceptions;
however, she may approach the scene with competing hypotheses rather than
a single hypothesis. For instance, what evidence do I expect to find assuming
either (1) 
 
this crime was committed by this person 
or (2)
 
 this crime was
committed by some other person.
If it is accepted that we can and should look
with purpose, then we must ensure that one of the purposes is to search for
inculpatory evidence (evidence that supports our primary hypothesis) as well
as exculpatory evidence (evidence that supports some other hypothesis).
The environment in which evidence is found must be taken into consid-
eration before we determine its relevance to the crime. Like hair, fibers are
ubiquitous in our environment, and their presence at a crime scene is
expected. Simply detecting a particular fiber, or even finding matching fibers
in reference and evidence samples does not 
 
a priori
imply their connection
to the crime. The case of 
 
People v. Morin
(Commission on Proceedings
Involving Guy Paul Morin
 
,
1998), illustrates how easily one can become
misled by failing to consider the circumstances of the case. Fibers prove