Edgeoscopy / Poroscopy
A reminder that there is more than just the Galton details.
By: John Schurman
Admin. Advanced Latent Fingerprint Training
FBI Academy Quantico VA.
January 2004
Over the past several years books and scientific journals have emerged about the friction skin of our hands, fingers, soles and
toes. Not only there use in identification but also the uniqueness and permanence of the skin. With emphasis on friction skin,
studies with anatomy, embryology and genetics has confirmed and enhanced the science of fingerprint individualization.
Friction ridged skin is a highly specialized organ. Friction skin is different than the skin on the rest of the body. Other
than its ridged appearance, it has no hair follicles and no apocrine or sebaceous glands. Friction skin has orderly rows of
eccrine (sweat) glands that are distributed three times greater than other areas of the non-friction ridged skin. Friction
skin is thickened and contains more nerve endings than the other skin of the body.
The function of sweat glands in other parts of the body is to dispose waste and to cool the skin surface by evaporation.
Sweat glands in the friction skin area seems to be activated more so when a person is nervous or in warmer environments. There
purpose of the sweat glands on friction skin is to remove waste and to increase friction by adding moisture on the surface of
the ridged skin. The increased friction slows or stops slippage.
The two main layers of skin on the palms, fingers, soles and toes is the inner area called the dermis and the outer called the
epidermis. The thickness of the skin varies considerably in different parts of the body. The proportions of epidermis and
dermis also vary. The palms and soles have a relatively thickened epidermis in addition to a thick dermis. Structurally the
volar areas (hands and feet) are different from the thin epidermis present elsewhere.
As the dermis has a connective tissue role among other things that won�t be elaborated in this paper, the epidermis will be
elaborated more as we move closer to the unique and permanent biological value of the small minute areas of the ridges and
pores.
The formation of the friction ridges are dependent on many issues such as genetics, shape and size of the volar pads before
birth, tensions and pressure of the environment while the skin is forming.
The friction ridges are not just sitting on the surface of the skin, they start deep within the lower area of the epidermis from
a cell which is a single columnar cell called the basal cell or stratum basal. The basal cell splits. This type of cell
division is called mitosis. The basal cell, which is the generating cell layer, divides and pushes the cells upward. The
cells journeying to the top layer change in appearance as they flatten. These changes of flattening in various stages give us
the other layers of skin. Such as in order from the basal cell: spinous, granular, hyaline and the horny layer also called the
stratum corneum. Cell movement from the basal to the horny layer takes approximately 30 days before the cells slough off the
skin. During the cells journey they are connected around all areas of the individual cells by a substance called desmosom.
The desmosom is a biological type superglue acting as an intercellular bridge joining the cells together. This joining prevents
cells shifting from the generating basal cells, the blueprint of all details of our friction skin, pore locations etc. Damage to
the epidermis such as cutting or scraping is about 30 days or less and is temporary unless the basal cell is damaged. Upon
damaging the basal layer mitosis still takes place; however, the mutilation to the basal layer upon healing produces a scar,
which will proliferate to the top layer as all other cells. The basal cells lying under the center of a friction ridge tend to
proliferate (move) at a faster rate than the cells to the side of the friction ridge or under the furrows. The details, however
minute, are all rooted in the basal cell.
Non-biological structures can change over time never to return to its original state. A vehicle tire for instance has a type
and size, molded from rubber mixtures. The tires leave tracks in snow, mud, etc. Matching the details from damage or wear done
after the tire was produced makes the identification of the track to a known tire such as missing areas of tread and the finer
areas of that damage. However, over time the tire wears away with changes that cause damage until loosing what once was there
to positively match know to the unknown tire impression.
Biological structures are unique in the fact that biology is a part of nature. Nature is the sum total of anything that
naturally occurs in the universe. I�ve heard and read that no two snowflakes are alike in its smaller details, or two trees
with the details of branch locations, direction, or the finer details of the bark or vein structure of a leaf. Although
snowflakes aren�t biological, it is the randomness of nature. Nobody has ever found any two structures in nature to be
identical in all detail. Nature is unique; therefore, biology is unique; therefore, people are unique; therefore, friction
ridge skin is unique. The natural parts that make up unique nature will all be unique in their own structure form and
feature.
When two fingerprints are compared for positive absolute individuality, all details are compared. Fingerprint identification
is the only discipline that has positive ID. Fingerprint science is totally objective and exact. Conclusions are absolute and
final. Others must be able to see what an examiner sees.
The comparison of a known print and an unknown print is broken down into three basic levels. The overall patterns, which are
arches, loops and whorls. The second is specific ridge path and the third is the detail of ridge formations such as ridge
shapes (Edgeoscopy) and relative pore locations and shapes (Poroscopy). The focus of this paper is on the third level of
comparison, Edgeoscopy and Poroscopy.
Poroscopy and Edgeoscopy are of tremendous value in the individualization process within the comparison stage of ACE-V. An
acronym for analysis, comparison and evaluation. Verification is from an independent examiner that starts from the beginning
of the methodology. In the past there was a general feeling that Poroscopy had little value because of the minuteness of the
detail and the failure of the pore structure to develop or reproduce consistently. Poroscopy was accepted in theory but ignored
in practice.
The science of Poroscopy was established by Dr. Edmond Locard from Lyons France in 1912. Locard believed that friction ridges
could be identified by comparing the pores based on size, shape, relative position, and frequency of appearance. The technology
today to develop ridge prints has improved where pores are appearing more frequently in ridge detail from crime scenes with use
of chemicals while not filling in the pore locations with powder. Of the three levels of detail mentioned earlier one should
not be used without the other. For example, an identification cannot be based on overall pattern without the using the specific
ridge paths of level two. If level three is present (clarity) ridge shapes and pore locations should not be ignored. Although
there is no mandate of a specific number of Galton details for an identification, the accumulative value of agreement in either
level two or three establishes a greater value for individualizing an area of friction skin.
While Dr. Locard established the uses of pores individualizing fingerprints, Salil Chattergee coined the term �Edgeoscopy� and
published a paper in the Fingerprint and Identification in 1962 and again in his book Finger, Palm and Sole Prints in 1967.
Chattergee�s idea was to use the ridge edges along with other friction ridge skin formation to individualize fingerprints.
The edge shapes of friction ridges are produced by differential growth and sometimes a shape is caused by a pore located near
the edge or between two pore locations opening into a furrow from the ridge. Edgeoscopy has always been part of friction ridge
comparison but cannot be used alone. The third level detail of ridge shapes only enhances comparison and improves ability to
describe how identifications are carried out. The formation of friction ridge characteristics, (second and third level detail)
found together in sequence with sufficient uniqueness to individualize is the philosophy of how much does it take to identify a
fingerprint and all friction skin.
The smaller the detail the more value for individualizing. It isn�t just the Galton details it is also what is between the
details.
Bibliography
1. Quantitative � Qualitative Friction ridge Analysis. David R. Ashbough. By CRC Press LLC 1999.
2. The Science of Fingerprints. Federal Bureau of Investigation. Rev. 12-84 by U.S. Government Printing Office Washington D.C.
3. Bailey�s Textbook of Histology 16th Edition pg. 366 � 377.
4. Poroscopy, Identification News November 1982. D.R. Ashbaugh CPL pg 3-8.
5. Ridgeology, Journal of forensic Identification. 16/41 (1) 1991 by David R. Ashbaugh.
6. The Detail, Internet news letter 12/10/2001. By John VanderKolk. Pg 1-4 http://clpex.com
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