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Fingerprints Do Not Lie (The following is an article which originally appeared in the FBI Law Enforcement Bulletin, Sept. 1969) The October 1968 issue of the Legal Aid Briefcase, a publication of the National Legal Aid Defender Association, featured an article entitled “Some Fingerprints Lie.” This concerned a murder trial in which a defense witness testified that a latent fingerprint found on the headboard of the victim's bed was not identical with the finger impression of the defendant, although two prosecution fingerprint experts testified that the latent print was identical with the fingerprint of the defendant. The defendant was found not guilty. While no attempt is being made here to question the merits of the verdict in this case, one part of the evidence concerned fingerprint identification and the referenced article attempts to cast serious doubt on the infallibility of fingerprint evidence. FBI fingerprint experts have since examined the fingerprint evidence in this case and found that the latent fingerprint is identical with the fingerprint of the defendant, and, also, that two of the points of identity indicated on the exhibits used in court were erroneously charted. FBI experts located and charted 24 points of identity on photographic enlargements of the latent and inked fingerprints. Professional Microscopist The defense fingerprint witness, who described himself as a professional microscopist (one who examines materials under a microscope), was retained by the defense counsel to rebut the fingerprint testimony of one of the prosecution experts. He testified that, after viewing the latent fingerprint in question through a 25--power binocular microscope, and after conducting his own examination, he determined that the latent fingerprint from the bed was not identical with the known fingerprint of the defendant. He claimed he was able to locate the 14 points of similarity testified to by the first police expert, but, after examining the prints under his 25--power microscope, he found “three distinct and crucial differences in the prints submitted.” An additional latent fingerprint of the defendant was found on a beer glass at the scene of the crime. It is interesting to note that the defense fingerprint witness concurred with the prosecution witnesses' identification of this print with a fingerprint of the defendant, although the quality of the fingerprint from the headboard, which he said was not identical, is better than the quality of the latent fingerprint removed from the beer glass. Matching Points The microscopist contended that, in effecting an identification of two prints, it is necessary to have as many matching points as possible, which may range from “one to a thousand.” It is a commonly observed fact that most fingerprints, even when nearly complete, would normally contain only from 75 to 150 identifiable ridge characteristics. He testified that regardless of the number of matching characteristics present, one point of dissimilarity would result in the conclusion that the two fingerprints are not identical: that is, that they were not made by the same finger. FBI fingerprint experts state unequivocally that any two fingerprints possessing as many as 14 identical ridge characteristics, the number which the defense witness acknowledged when he testified concerning the fingerprint in question, would certainly contain no dissimilarities in the ridge formation. In describing his fingerprint examinations, the defense witness claimed he used a geometric pattern technique of drawing lines between ridge characteristics to discover his “diversities.” which technique he claimed is employed by the FBI. This technique is certainly not used by the FBI, although it has previously come to our attention. It is not considered a valid method of establishing identity, as it can lead to erroneous conclusions. Our fingerprint experts point out that impressions made by the same finger may show considerable variation between the actual physical location of the ridge characteristics. This could be caused by many factors, such as twisting and pressure exerted when the latent impression is left on a surface or when an inked impression is being obtained from the finger, the degree of perspiration or oily matter present on the fingers, the nature or condition of the surface on which the latent print is left, or the adherence of powder used in developing the latent impression. Magnifying Glass It is ironical that the microscopist would use as one of his strong points the fact that he used a 25--power magnifying glass in examining the evidence. In reality 4 or 5--power magnifiers are far superior for classification and comparison purposes because such magnification offers the maximum contrast and sharpness of the very ridge detail which the fingerprint expert is observing. Frequently, fingerprint experts will, however, enlarge fingerprints 10 times or more in preparing charts for illustrative purposes in furnishing testimony for the purpose of demonstrating the fingerprint identification to the jury and others present in court who have a limited knowledge of fingerprint identification. Rebuttal Letter The June 1969 issue of The Legal Aid Briefcase published a letter dated April 23, 1969, from FBI Director J. Edgar Hoover rebutting the October 1968 article of this same publication. Fingerprint science is a positive means of identification, and in the hands of knowledgeable technicians and experts, it is a potent weapon in the continuing fight against crime. Fingerprints do not lie. (Editor --— The defense witnesses position that “regardless of the number of matching characteristics present, one point of dissimilarity would result in the conclusion that the two fingerprints are not identical: that is, that they were not made by the same finger” demonstrates his obvious confusion between Dissimilarities and Distortion .)
This article was reprinted in “THE PRINT” 10(5), May 1994, pp 3-4 |