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3.
Individualizing Characteristics
We have now established several points.
1. All physical objects are unique by virtue of their existence in space
and time.
2. Class characteristics are created by repetitive, controlled processes.
3. Individual characteristics are created by random, uncontrolled processes.
4. Both the source and any items originating from it commence to change
the moment they each begin an independent existence in space and
time. You should recognize this as one of the corollaries of divisible
matter from Chapter 4.
Thus, we can define an individualizing characteristic as
 
4.
Physical Evidence with Individualizing Potential
Over the years, both by default and design, analysts have collected large
amounts of empirical data about individualizing traits (e.g., Biasotti, 1959;
Pounds and Smalldon, 1975; Gaudette, 1978; 1982; Bodziak, 1990; Stoney
and Thornton, 1986a,b; 1987; Murdock and Biasotti, 1997; Nichols, 1997;
Grieve and Bermann, 1997; Houck and Siegal, 1999).* From these data,
criteria have emerged regarding the number and kind of traits required for
 
Individualizing Characteristics:
Traits that are produced by a random, uncontrolled process. 
They are used to individualize items to a common source.
* These references represent only a small sampling of the accumulated body of work
addressing individualizing traits. The population studies of serological and DNA traits in
biological evidence are too numerous to even begin to enumerate here.
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Principles and Practice of Criminalistics
a conclusion of common source. The formality of organization, breadth of
dissemination, and rigor of testing of these criteria have varied historically
for different disciplines. Nevertheless, criminalists agree that certain catego-
ries of evidence contain inherently individualizing potential:
• Physical match evidence
• Print and impression evidence
• Toolmarks of all kinds, including firearms
• Shoeprints (as opposed to footprints)
• Biological prints including fingerprints, footprints, and those from
other body parts, such as ears (van der Lugt, 1997; Burge and
Burger, 1999) and lips (Moenssons, 1999).
• Handwriting evidence
• DNA analysis of biological evidence
Although comprehensive numerical databases are only available for DNA,*
a large amount of qualitative data exists upon which examiners of compar-
ison evidence currently base their opinions.