“Ridgeology” is the study of the uniqueness of all friction ridge skin formations and their use as a means of personal identification.
Study of ridges have two parts:-. 1. Edgeoscopy; and 2. Poroscopy.
Edgeoscopy is the study of the friction ridge edges for their alignment and the shape of their individual ridge units, as well as the shapes and alignments of pores close to the ridge edges which appear as notches.
Most of the times, identity has to be fixed for the scene of crime (chance) prints. These chance prints may be partial, faint, smudged or may not have sufficient number of ridge details for establish an opinion. In India, after the First Director’s Conference of Forensics, held in Srinagar, in 1973, it was decided that the matching report will be given when eight ridge characteristics are found identical in nature and relative positions in the questioned print as well as in the specimen print. The least number of ridge characteristics required for fixing identity varies from country to country.
While researching the possibility(ies) of new methods of criminal identification, Salil Kumar Chatterjee, a great pioneer in the field of fingerprints, coined a new term *Edgeoscopy* through his papers published in Fingerprints and Identification in 1962 and republished in the second edition of his own book Finger, Palm and Sole Prints in 1967.
Poroscopy and Edgeoscopy are third level method of fingerprint identification through examination of the unique details and characteristics found along the edges of individual fingerprint ridges(for Edgeoscopy) and individual sweat pore situated on every epidermal unit which fuse together to form a ridge.
Characteristics shapes are exhibited on one or both sides if the friction ridges that appear often and they may be straight edge, convex edge, peak – edge, table edge, pocket edge, concave edge, angle edge, infinite edge, etc.
To establish identity, the edge characteristics in one side or both sides of ridges are combined with Galton details and pore positions un their relative positions.
Poroscopy is the study of the size, shape, relative position, arrangement and frequency of sweat pores. Poroscopy was established by Dr. Edmund Locard in 1912. Papillary skin contains an average of 2700 sweat glands per square inch of the skin surface. Each gland has an opening called sweat pore. According to Locard the agreement between 20 to 40 pores is sufficient to establish positive identification. The sweat pores vary in the following ways:-
- Size of pores – small, medium or large.
- Frequency of various pores.
- The shape of an individual pore – rounded, elliptical, rhomboid, square, rectangle, etc.
- Relative position of pore on the ridge – open type or closed type.
- Comparison of relative location of the pore.
Between the two fields of Ridgeology, the Edgeoscopy is used and studied more. At the time of impression being taken the pressure applied on the finger takes a toll of sweat pores whereas the edges of ridges are not affected drastically.