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Ashbuagh, Cpl. David R. Ridgeology: Modern Evaluative Friction Ridge Identification. Royal Canadian Mounted Police.

Abstract: Ridgeology refers to "a forensic identification science that is associated with all of the ridges on the volar areas and not just on the finger tips as Dactyloscopy or fingerprint identification implies." The paper provides a historical review of fingerprint identification and fingerprint science research. Currently, friction ridge identification methods encompasses all of the volar areas. The remainder of the paper explains the process of fingerprint identification.

The explanation begins with a discussion of the structure of fricition skin. On volar areas of the skin, the dermis is covered with double rows of peg-like formations called papillae. Each double row sits under a ridge that appears on the epidermis (the surface) of the skin. The furrows on the surface reflect the valley-like space between the two rows of derman papillae. In human evolution, these ridges developed as scales on early mammal skin lined up in rows and fused together (likely through mutation at first). Scales evolved into small wart-like bumps that then fused into rows, the predecessor of the friction ridge. Ridges formed in circles, as early mammals could turn 360 degrees on their footpads. The areas on volar pads we now see still have circles in the oldest weight-bearing walking pads of the extremity.

These pads develop on the fetus and can be affected by disease or birth defect. The paper outlines the development process in the womb and stresses that all ridge units are subjected to a variety of genetic and physical pressures while the fetus grows. Because the genetic and physical pressures vary so greatly, no two areas of friction skin will ever be the same, even in a small area. The substructure of the organization and number of papillae pegs changes over the life cycle (child-adult), but the primary ridges and the resulting surface friction ridges never change.

Because examining fingerprints is an intensive mental process, the article recommends that comparisons be done in when in a clear frame of mind and in a stable environment with minimal distractions.

Examining fingerprints compares similaries and details between a known and a questioned. The details will be a class characteristic or a unique or randomly placed characteristic. Class characteristics are the result of genetics, unique characteristics are created by the random growth of the friction ridges. Identification rests in ìa combination of corresponding or similar and specfically oriented characeristics of such number and significance as to preclude the possibility of their occurrence by mere coincidence, and there are no unaccounted for differencesî that allow a conclusion that the two samples are the same. Often, small details in simingly similar prints can be the difference

Details are found in three levels: pattern or ridge configuration which is a class characteristic; type and position of minutiae (dot, short ridge or island, encloser or lake, bifurcation, ridge ending) which are unique formations; and shape of minutiae, shape of individual ridges, presence and location of pores. Clarity of the print and quanity of detail can affect identification. Once a known and questioned are determined to have a common origin, it must also be determined that no other area of friction skin may have made the print (there must be sufficient uniqueness about the detail).

The methodology that allows these comparisons has three stages: analysis, comparison, and evaluation. Analysis is the examination of the unknown area of friction ridges and reduction of it into its basic components. Then, the analyzed questioned print is compared to the area of friction ridges on the known print. The comparison starts at a common location on both prints and the minutiae are compared to each other as to location, shape, and relative position. This comparison is systematic and sequential until all available detail has been compared. Then, evaluation gives a weight to similiarties and dissimilarities that is applied toward establishing individuality. Evaluation takes place during comparison and is an ongoing process. Overall pattern rarity, then unique characteristics are evaluated, including open fields. The better the detail, the greater the individualizing power. The experience of the examiner also plays a role. The examiner may then work with another examiner to provide verification for the conclusion.

The paper then discusses poroscopy and its use in fingerprint comparison. Although pores often do not appear in inked or lifted prints, as print developing technology advances, they are increasingly visible and used in identification. Pore position does not change and can be used in conjunction with ridge and minutiae analysis. Pore locations and ridge identifying marks can be marked on clear overlays and then the overlays compared between known and questioned. Care should be taken to note pressure distortion.

For more information, contact:
Royal Canadian Mounted Police web site: www.rcmp-grc.gc.ca/html/rcmp2.htm

 
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