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Embryology and Morphology of Friction Ridge Skin

The Fingerprint Sourcebook - Chapter 3


National Institute of Justice

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Introduction

Friction ridge skin has unique features that persist from before birth until decomposition after death. Upon contact with a surface, the unique features of friction ridge skin may leave an impression of corresponding unique details. Two impressions can be analyzed, compared, and evaluated, and if sufficient quality and quantity of detail is present (or lacking) in a corresponding area of both impressions, a competent examiner can effect an individualization or exclusion (identify or exclude an individual). The analysis, comparison, evaluation, and verification (ACE-V) methodology, combined with the philosophy of quantitative–qualitative examinations, provide the framework for practical application of the friction ridge examination discipline. But at the heart of the discipline is the fundamental principle that allows for conclusive determinations: the source of the impression, friction ridge skin, is unique and persistent.

Empirical data collected in the medical and forensic communities continues to validate the premises of uniqueness and persistence. One hundred years of observations and statistical studies have provided critical supporting documentation of these premises. Detailed explanations of the reasons behind uniqueness and persistence are found in specific references that address very small facets of the underlying biology of friction ridge skin. This chapter brings together these references under one umbrella for the latent print examiner to use as a reference in understanding why friction ridge skin is unique and persistent.

The basis of persistence is found in morphology and physiology; the epidermis faithfully reproduces the three- dimensional ridges due to physical attachments and constant regulation of cell proliferation and differentiation. But, the basis of uniqueness lies in embryology; the unique features of the skin are established between approximately 10.5 and 16 weeks estimated gestational age (EGA) due to developmental noise.

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