ABSTRACT

A. In the Beginning ..................................................................................... 84 B. The Nature of Matter ............................................................................. 86 C. Divisible Matter — A New Fundamental Principle in Forensic

Science ..................................................................................................... 87 1. Properties Useful for Source Determination................................. 88 2. Properties Confounding Source Determination........................... 89 3. More on the Nature of Matter: Thermodynamics and

Entropy............................................................................................. 91 4. An Example of Divisibility ............................................................. 92 5. Impression Evidence — Does Divisible Matter Apply?................ 93

D. Transfer Theory (Locard)....................................................................... 93 1. Physical Transfer.............................................................................. 94

a. Trace Evidence — Transfer of Very Small Physical Entities ...................................................................................... 95

b. Macroscopic Evidence — Transfer of Larger Physical Entities ...................................................................................... 95

c. Factors Affecting Transfer and Detection............................... 95

2. Spatial Trait Transfer ....................................................................... 96 a. Impression Evidence ................................................................ 96 b. Three-to Two-to One-Dimensional Transformations......... 96

E. Summary ................................................................................................. 98 References ........................................................................................................ 99

The cornerstone of forensic science since the early 1920s has been a maxim attributed to Edmund Locard. It appears in two or three permutations in his writings, but the most comprehensive statement translates as follows:

Locard himself never proffered this as a principle; his students and colleagues were the ones who transformed this simple

raison d’être

into a foundational principle of forensic science. In the process, Locard’s musings were transformed into the definitive, “Every contact leaves a trace.” In the same way that Quetelet’s “Nature exhibits an infinite variety of forms” was adulterated to “Nature never repeats herself” (Thornton, 1986) subtle but important differences exist between Locard’s original quote (1920) and the modern redux of it. Among other distinctions, the redacted version retains no mention of a crime; the reader is left with the impression (whether correct or not) that transfer is equally likely and equally important under any circumstance. Further, Locard implies that the criminal is acting under stress and with anxiety (“the intensity that the criminal act requires”). This leaves no room for the psychopathic criminal who feels no emotion whatsoever in the commission of a criminal act, and so does not experience the type of stress and anxiety implied by Locard. Nor does it allow for the serial criminal, who may perfect the crime’s

modus operandi

with each new commission of it, reducing the chances of leaving traces behind. Neither Locard’s original

writings nor current interpretations explicitly address the possibility of transfer in both directions, although one might argue that Locard implies it. Our expectations with regard to cross-transfer impact on both the search for evidence and the interpretation of that which is found. For example, an expectation that two-way transfer should occur might weaken an association for which traces of contact are not found in both directions.