Forensic Fingerprint Analysis

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The understanding of the formation of friction ridge skin and the permanence of fingerprints is imperative to the criminal investigator. Fingerprints never change (apart from temporary abrasion and permanent scarring). The understanding of friction skin growth during the fetal development period is necessary for anyone doing fingerprint analysis.

Friction ridges develop on the fetus before birth. Friction ridge skin is the skin on the palms and fingers of the hand and soles and toes of the feet. Friction ridge skin has ridges and furrows between them. This surface helps individuals to grasp and hold onto items. The ridges are formed three to four months into fetal growth. Fingerprints are constant. They never change unless there is permanent scarring that occurs. The ridge patterns are unique and are never repeated.

The embryonic skin begins to form at 4-5 weeks of fetal growth. Volar pads (the pad of your fingers) are developed somewhere between 6.5 and 10.5 weeks in fetal growth. By the 9th week, the volar pads vary by position and shape. The development of the volar pads coincides with the epidermal ridges.

We know that by 8 weeks, the epidermis is strongly constructed. Scientific research has shown that the developments of epidermal ridges are preceded by the formation of volar pads. The five digits develop about one week after the development of the volar pads.

“The number of primary ridges increases as new ridges are formed between or at the
lateral surface of existing ridges. Primary ridges proliferate rapidly to keep pace with
the increasing separation of adjacent ridges due to general growth of the hand. This
proliferation produces the branchings and islands, the minutiae. As primary ridges begin to develop, they define the basic ridge configurations of the volar skin surfaces. However, these configurations develop at the epidermis-dermis interface and not on the skin surface. As the number of primary ridges increases, the ridges continue to increase in dimension. Primary ridges increase in width and penetrate deeper into the underlying dermis.”
Around 15 weeks of fetal development, secondary ridges form. These secondary ridges follow the same pattern as the furrow at the surface. By 24 weeks of development, the fetus has the same markings comparable to what it will have as an adult. On the volar surface (palm aspect), the epidermal ridges can be seen as fingerprints.

Many factors affect the tension across the skin, thus a unique pattern of ridge occurs. This ridge can never be duplicated. Ridge shape forms based on the “distribution of basal cells along the basement membrane”

Referenced from http://www.clpex.com/Articles/TheDetail/1-99/TheDetail09.htm

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