Encyclopedia of Psychology and Law

cause the anomalies that become a part of the config-

urations within natural pattern structures. All natural

patterns in volar skin will be unique. This includes the

ridges, furrows, creases, and pores and their anom-

alies and textures that make up the skin. Scarring will

provide new unique features to the skin. The homeo-

static regeneration of skin maintains the form and

function of the features of the volar surface in persis-

tent configural and sequential arrangements.

Basis of Testimony

The uniqueness and persistence of friction ridge skin is

the rule of support for the proposition that an individ-

ual can be determined as having touched a particular

surface. With this rule or law, the next step is to exam-

ine the latent and standard prints and determine

whether the latent print was made by the person who

made the standard print. The two prints are compara-

tively measured with each other. The first-level detail

of general direction of ridge flow is examined, fol-

lowed by examination of the second-level detail of

lengths of individual ridge paths with their endings and

bifurcations and, if needed, the examination of the

third-level detail of edges, textures, and pore positions

of the ridges. The details are examined to determine

whether they correspond in sequences, shapes, and

configurations in both prints. The examination results

either in a determination that the person made the

latent print (individualization) or that the person did

not make the latent print (exclusion), or no determina-

tion is made whether the person made the latent print

(inconclusive). This individualization or exclusion

determination has, in principle, a philosophical prob-

lem: Comparisons between the latent print and all

prints in the world are impractical. However, in prac-

tice this has been overcome with a high degree of cer-

tainty (although there are criticisms of this conclusion,

which we will discuss in a later section). The expert

makes the determination that there is definite agree-

ment between the configural and sequential arrange-

ment of details in the two images, indicating that they

were made by the same unique and persistent source.

The individualization decision basically comes down

to the expert judgment that the recovered latent print is

so similar to the inked print that it could only have

come from the same person. Stated in a different way,

the claim is made that there is no more similar print

from any other source among all the prints in the

world, which is of course impractical to test. In practice,

the individualization often comes down to the expert

rendering the opinion that the degree of match between

the latent and the inked print is typical of known train-

ing, competency, and proficiency individualizations and

casework peer-reviewed individualizations and is closer

than any close correspondence from another source that

the expert has ever seen or expects to see. Because this

judgment is based on prior experience, presenting a con-

clusion in court depends on the expert establishing his or

her credentials, which has become a major portion of

latent print testimony and is discussed next.

The latent print expert examiner should have some

basic knowledge before conducting case work, ren-

dering conclusions, and testifying in court. This

includes understanding the source of images, volar

skin, and its unique and persistent features. The exam-

iner also must understand the basics of fetal develop-

ment, homeostasis, growth, aging, wound healing,

scarring and imperfections of the volar skin, and the

uniqueness of pattern formations in nature. Moreover,

the examiner must understand distortions of the skin

and variations in appearances of latent or standard

prints or images. Latent and standard print develop-

ment, capture, and imaging techniques must be under-

stood to understand the variations in appearances. The

examination method within the latent print commu-

nity of analysis, comparison, and evaluation (ACE),

possibly followed by verification (V), is the method

used in conjunction with the sufficiency and judgment

threshold of quality and quantity (QQ) of details in the

images. Furthermore, the examiner must understand

examination method and sufficiency and judgment

thresholds. In addition, the examiner must understand

the history of latent print examinations and latent print

communities, the role of a community within science,

and the role of the expert within a scientific commu-

nity. Finally, the latent print examiner must be trained

to be competent and demonstrate accuracy and profi-

ciency within the community.

The goal of an examination is to judge whether

developed unknown latent prints and known standard

prints are sufficient for examination purposes and

whether the considered source of the latent print can

be determined or excluded. As noted earlier, three

conclusions of the comparative examination can be

reached: (1) the unknown print was determined to

have been made by a specific source or person (indi-

vidualization); (2) the unknown print was determined

not to have been made by a specific source or person

(exclusion); (3) no determination was made whether a

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