|
|
|
Poroscopy: An Overview (The following article is reprinted from the Apr.--Jun 1995 issue of the T.D.I.A.I. newsletter. Texas seems to generate a bountiful supply of original material--—Thanks again)
by EUGENE CZARNECKI Over the past years, scientists, doctors, police officers, and people in general have been interested in finding a method of identifying people by means other than general outward physical features. They have been searching for some unique identifying set of characteristics. A variety of different methods have been suggested, the Bertillon Method, “retinal blood vessel configurations in the eye"1, DNA, and fingerprints. We will be examining a specific aspect of the “science of fingerprints” referred to as “ridgeology”. Ridgeology is the examining of two parts of the ridge of the friction skin surface, the pores and the edges of the ridges. Each respective study has it's own name, poroscopy and edgeoscopy. To help clarify these two terms we will use Scott's Fingerprint Mechanics, “poroscopy is the term applied to a specialized study of pore structure found on the papillary ridges of the skin as a means of identification2, and “edgeoscopy is a term applied to the study of the characteristics formed by the sides or edges of the papillary ridges as a means of identification"3. These definitions were given to add a little more insight, but we are going to deal strictly with the area of poroscopy. The pore sets on top of the ridge. It's physical purpose is to provide a liquid cooling system for the exterior of the human body. Various types of waste is carried with the liquid that is expelled through the pore during this cooling process. The palmer surfaces, palms and finger, and the plantar surfaces, soles of the feet and the toes, have an average of 2700 pores per square inch of ridge friction skin surface. This compares to approximately 400 pores per square inch of the balance of the body's skin surface. These pores help differentiate the ridges used in comparison, to “incipient ridges” that appear between the ridges used for identification. The basis used for the comparison using pores is based on the different shapes, sizes, distance from each other, and the distance from edges. This comparison principle is essentially the same that is used in the comparison of latents using “Galton details”. Roughly, there are nine to eighteen pores per centimeter of ridge. Dr. Edmond Locard, a French Criminologist, first practiced poroscopy. He is reported to have made the first identification based on poroscopy in 1912. Cpl. David Ashbaugh of the Royal Canadian Mounted Police later examined the chart Locard had made for this trial. Ashbaugh later wrote, “The print that Locard illustrated contained a large number of minutiae detail which would have been sufficient for an identification"4. The case was commented on by Capt. Douglas E. Walsh of the Fort Worth Police Department. Walsh had spoke to the International Association for Identification at it's annual convention in Fort Worth in 1939. Walsh related to the convention, “Poroscopy....is destined to become a vital factor in law enforcement because of it's positive identification value and since it has already been accepted by the higher courts as positive proof. Thus, the courts have set a precedent as to it's value”5 Captain Walsh also cited that a “tiny fingerprint pattern could contain 1,000 pores and that while the fingerprint pattern might be insufficient for a positive identification, the pores within it could prove an identity conclusively”.6 Based on a postulant, the latent print identification must stand on it's own for it to be a valid identification, did Locard hope to subconsciously convince the people at the trial he testified at that he was right in the explanation of poroscopy? Did he display a large photograph so that everybody who saw the comparison was easily convinced of the match? Ashbaugh leaves me wondering, if Locard used this case to prove his study or theory, just because it has so many “Galton Points” to fend off any challenge him? Not that many other experts in fingerprints were readily available in town. Regarding the case of Captain Douglas, he remarks that 1,000 pores would be sufficient. Mathematically, in our minds, compare an area of 1,000 pores to the possibly 2,700 pores per square inch of ridged friction skin surface. This figures out to be 0.37 square inches of ridged friction skin surface. This area would be a rectangle one inch by (approx.) three--eights of an inch. I would think a number of “minutiae” for identification could be found in such an area, especially if one had a perfectly developed latent and a perfectly rolled inked impression card to compare with it for high accuracy.
Many factors must be taken into account when one looks at poroscopy. The
outside factors are many, consistency of ink, type of surface holding the
ink, consistency of the physical makeup of the card or media to hold the
inked impression, ink spreads like water on a sponge when placed on paper.
The accumulation of debris on the paper and what it is place on Human factors now enter the picture. The amount of pressure phenate [sic] by the subject being studied, and the person applying the ink. The amount of pressure applied by both parties when the inked impression is being made. Currently, it is difficult enough to get clear and equally dark rolled inked impression cards for latent print comparison. Outside factors that effect the human skin can take place that could change the pores. Dirt on the surface, minor cuts or abrasions slight enough to change the shape of the pore(s) for a very short time. The mental condition at the time of the commission of the offense, or when the rolled inked impressions of the skin surface area are made. They could be sweating with the pores very dilated at one time, and nothing at the other time. Weather conditions, such as temperature and humidity, could change the pores. Cold or cool conditions would make the skin expand. Biological factors in skin changes would change the area that one might be looking for a “pore comparison”. These changes could be warts or growths, and amputations or even scarring. These types of changes represent a total change in the uppermost layer of skin. The temporary effects, such as dirt, could easily transfer to and be developed in the latent. A small particle of dirt would make a pore that was surrounded by ridge appear as though it was on the edge of the ridge. The crime scene technician dusting the scene may not clean the developed latent perfect enough to expose the pores. A large number of factors enter into this “science of poroscopy”. The more “questionable factors” that enter into the examination, the more one has to look to explain away these factors. If one has to sit on the witness stand and attempt to explain away various differences, it may be viewed as though they are making excuses. This type of testimony lends itself to be doubted. One of several writers convey the following, “the most practical potential value of the comparison of pores or edge contours would be their use as additional evidence of identifiers, were the more traditional characteristics are quite limited but the print is otherwise well recorded”7. I am of the belief that each identification must stand on it's own. It would be up to the individual latent examiner if they would want to wander into this area of “poroscopy”. It would be a decision that would have to be weighed very carefully, and with much deliberation.
1 Dilworth, Donald C.: Identification Wanted: Development of the American Criminal System 1893--1943: (Gaithersburg, Md., International Association of Police) 202. 2 Scott, Walter R.: Scott's Fingerprint Mechanics, edited by Robert D. Olsen, Sr.: (Springfield, Il. Thomas, 1978d), 30. 3 Ibid., 34. 4 David R. Ashbaugh: Ridgeology (Modern Evaluative Friction Ridge Identification): Canada, 32. 5 The Detective, September 1939; quoted in Donald Dilworth, Identification Wanted: Development of the American Criminal System 1893--1943, (Gaithersburg, Md., International Association of Police, 1977), 202. 6 Ibid. 7 James F. Cowger: Friction Ridge Skin: Comparison and Identification of Fingerprinting: (New York: Elsevier, 1983), 143. (Editor--— In addition to a valuable overview of poroscopy, this article mentions a couple of topics worth further discussion. The author suggests that “A small particle of dirt would make a pore that was surrounded by ridge appear as though it was on the edge of the ridge” and other factors which “could change the pores”. These are topics which have received some debate and are deserving of further literary review.)
This article was reprinted in “THE PRINT” |