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