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particular, a scientific framework for forensic thinking has not been well
articulated. We present such a framework in this book. It is our hope that
this contribution will assist journeymen criminalists to, at the very least,
understand their specialty within the greater context of a case investigation.
 
C.
Evolution of Concept
Although a few core concepts have been articulated by thoughtful individuals,
the field of criminalistics has operated for most of its tenure without a
comprehensive paradigm. The maturation of the discipline, and a full mea-
sure of respect from the scientific community, requires the development of
a unifying framework specific to the practice of forensic science. The follow-
ing section traces the evolution of integral but fragmented concepts such as
transfer and individualization. In the next chapter, we present a unified
paradigm that incorporates those concepts as well as others.
1.
Transfer
To become evidence, material must first be transferred to or from an item
relevant to the crime. This concept has been historically understood in terms
of trace evidence such as particles and fibers. Implicit in the understanding
of the concept has been the assumption that the transfer is inadvertent and
* Although a number of American universities offer the opportunity to perform doctoral
research in forensic science or criminalistics under the umbrella of a criminal justice or
chemistry program, at this writing, none has a full-fledged doctoral program in forensic
science.
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44
Principles and Practice of Criminalistics
unheeded. Edmund Locard is universally credited with articulating the concept
of “exchange” or 
transfer
as “every contact leaves a trace.” Because most of
Locard’s writings were in French, tracing the origin of this aphorism has been
somewhat circuitous. The most likely candidate appears to be a passage from
L’enquete criminelle et les methodes scientifique
, published by Locard in 1920.
The original passage in French is reproduced below with an English translation
following. We’ve left the grammatical alternatives provided by the translator.*
Nul ne peut agir avec l’intensité que suppose l’action criminelle sans laisser
des marques multiples de son passage, tantot le malfaiteur a laissi sur les lieux
des marques de son activité, tanto par une action inverse, il a emporti sur son
corps ou sur ses vetements les indices de son sejour ou de son geste.
No one can act [commit a crime] with the force [intensity] that the
criminal act requires without leaving behind numerous signs [marks] of it:
either the wrong-doer [felon; malefactor, offender] has left signs at the scene
of the crime, or, on the other hand, has taken away with him — on his
person [body] or clothes — indications of where he has been or what he
has done.
Locard was the first to undertake an extensive study of “dusts,” “mud,”
and “grime.” His mentor at the University of Lyons, Alexandre Lacassagne,
was among the first to propose the study of dust on clothing or body parts
as an indicator of occupation and whereabouts (Thorwald 1966). Locard had
also been exposed to the writings of Hans Gross and French translations of
the Sherlock Holmes stories. He gives due credit to both these sources as
inspiring his dust investigations (Locard, 1928). Just about the time that
Doyle, tired of writing and fresh out of ideas, sent Holmes plunging into
Reichenbach gorge to die what later turned out to be a quite virtual death,
Gross had just finished 
Criminal Investigation
. Although it is unclear if either
he or Doyle were influenced by the other, they were unique in their time in
suggesting that microscopic evidence — what we now call trace evidence —
could provide valuable clues to the solution of crime.
In early 1910, when Locard had just established his Lyon laboratory and
begun his enormous effort to catalog dusts, “scientific criminology” was
occupied with the shift from anthropometry to fingerprints. Although
Locard’s thoughts on dust were initially ignored by police officials, his suc-
cessful solution of several crimes finally caught their attention and produced
funding and support (Thorwald, 1966). By 1920, Locard had completed his
encyclopedic work of cataloging and classifying the microscopic and micro-
chemical characteristics of various dust particles (Thorwald, 1966). Whether
or not he ever uttered the exact phrase that we now quote as representing
* Translations courtesy of Sharon Kruzic.
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The Evolution of Forensic Science
45
the principle of transfer, he is certainly to be credited with inspiring and
disseminating it.
Other than an occasional quoting of the “exchange principle,” there does
not appear to be evidence of any great intellectual progress in this area until
Paul Kirk revived its consideration in the 1950s. Kirk was among the first to
consider the strength and significance of trace evidence. He performed stud-
ies on the occurrence and transfer of fibers in urban environments (Kirk,
1953). Although the concept of transfer is universally accepted today as key
to the understanding of forensic evidence, very little has been done since
Kirk to explore its consequences, establish its limitations, or specifically relate
it to various types of evidence. There has been no consensus regarding how
the strength of an association established by transfer evidence should be
determined, nor how its significance might be understood in the context of
a case. With the increasing expectation that experts provide a rigorous sci-
entific basis to support their opinions, it will be interesting to see how the
trace evidence community meets this challenge. Certainly an excellent start
has been made with the guidelines put forth in 1999 by the Scientific Working
Group in Material Analysis and Testing (SWGMAT). We will discuss the
concept of transfer in depth in Chapter 4, including some aspects of transfer
that are not usually considered, such as “macro-transfer.”