Identifying criminals using fingerprint impressions found at crime scenes and comparing them to known fingerprint files collected as a result of previous criminal activity has been used by police services around the world for over 100 years. Not all people believe, however, that fingerprint identification is a science and therefore should not be used as a means to identify or individualize.
A landmark 'science of fingerprints' case in the courts occurred in 1911 in Chicago, U.S.A. It resulted in the conviction of a man named Thomas Jennings for murder. Very little evidence against Jennings existed ...the most significant being fingerprints. To ensure that fingerprint evidence would be admitted, the prosecution called several recognized fingerprint experts as witnesses. Edward Foster - the man responsible for the establishment Canada's national fingerprint bureau - was one of these witnesses. With the help of his testimony, Jennings was convicted and sentenced to hang on December 22, 1911.
What was the scientific basis for allowing fingerprint evidence for this case?
At the time, it was the research and comprehensive book Finger Prints published in 1892 by Sir Francis Galton, a well-known scientist, that made a significant contribution to the science of fingerprint identification. "Galton's more interesting contribution was his method of distinguishing fingerprints that contained similar patterns. The general fingerprint patterns of twins, for example, were often the same. But Galton had noticed that fingerprint ridges did not proceed across the fingertips in unbroken lines. They often stopped abruptly, split, contained enclosures, or connected with other ridges. The arrangement of these ridge details were never repeated in a print from two different fingers, not even in twins. Identification of one fingerprint with another, Galton realized, should always be made by comparing their ridge detail or fingerprint minutia (known later as points of comparison or identification). He used this comparison of ridge detail to confirm Herschel's observations of fingerprint permanence." (Copyright C 2001 Colin Beavan) As a result of his research Galton confirmed that a person's fingerprints would identify him for life and he "became sufficiently confident in the method to say that it would indeed form the basis for a reliable system of identification."(Copyright C 2001 Colin Beavan)
Galton also proposed a statistical model in an attempt to provide a scientific basis for the uniqueness of fingerprints and therefore justify their use in identification. Pat Wertheim explains, however, that "Galton's model overlooked any consideration of the direction of ridge flow in any of the 35 grid areas and took into account only whether or not a minutiae point was present in any given square. Obviously, Galton's model completely ignored not only ridge flow, but also the shapes of the ridges, the presence of prominent sweat pores, scars, creases or wrinkles, incipient ridges etc...Thus, Galton's model was sorely lacking in many respects." (Scientific Comparison and Identification of Fingerprint Evidence, July 2000 issue of Fingerprint Whorld.) Had Galton approached his research from the belief that all human beings are unique and therefore our fingerprints are different - rather than the other way around - he would have realized the 'extreme difficulty' in placing a value on the uniqueness of nature. Nevertheless, Galton's work provided "the systematic proof of its scientific basis" (Copyright C 2001 Colin Beavan) and advanced the science of fingerprint identification significantly.
The defense lawyers for Jennings's appealed his conviction to the Supreme Court of Illinois, arguing that fingerprint evidence should not be accepted. "In this first test of the legality of fingerprints in an American high court, the landmark ruling stated that, "there is a scientific basis for the system of fingerprint identification, and...the courts are justified in admitting this class of evidence. The Illinois Supreme Court's ruling was thorough and comprehensive. It included a complete outline of the history and practice of fingerprint identification." (Copyright C 2001 Colin Beavan)
"The Jennings case gave fingerprinting another boost toward its universal acceptance around the world..." (Copyright C 2001Colin Beavan) This, of course, lead to fingerprint comparisons being completed by law enforcement personnel for the purpose of identifying criminals. Fingerprint evidence was now well on its way as being accepted by the courts with very few challenges over the next 100 years...until now.
David Ashbaugh, in his book Quantitative-Qualitative Friction Ridge Analysis, May 1999, states, "It is difficult to comprehend that a complete scientific review of friction ridge identification has not taken place at sometime during the last one hundred years. A situation seems to have developed where this science grew through default...The failure of the identification community to challenge or hold meaningful debate, can also be partly attributed to the fact that the friction ridge identification science has been basically under the control of the police community rather than the scientific community."
Perhaps this was a problem that was foreseen by Henry Faulds, the Scottish physician who also completed extensive fingerprint research and was the first to propose the idea of using fingerprints as a means of criminal identification. Faulds criticized Inspector Charles Collins of Scotland Yard who compared an inked fingerprint with a bloody fingerprint found on a cash box and concluded that there were eleven matching "characteristics". The inspector's testimony at the 1905 Deptford murder trial helped to convict the two men accused of murdering Ann and Thomas Farrow.
"Faulds had compared many thousands of fingerprint sets to satisfy himself that no ten fingerprints could be duplicated on two different people. He complained publicly that no one, including the Yard, had made a similar comparative study to prove that each single fingerprint was unique. Until this was done, he insisted, no man should be sent to the jailer or the hangman on the basis of a single fingerprint, particularly one identified by the Yard's Fingerprint Branch. Ever since the Branch had denied Faulds's part in the fingerprint conception, Faulds had bitterly questioned its integrity. It didn't help the Yard's case that Faulds delivered his arguments with the force of a man who had been scorned. It didn't help, either, that science didn't have the foothold in the courtrooms that it does today." (Copyright C 2001 Colin Beavan)
We know today that friction ridge identification is an applied science. Scientific research by the scientific community over the last 100 years and observation by scientists and friction ridge identification specialists have supported this fact. The science of friction ridge identification would benefit greatly however from implementation of higher standards in training and in developing procedures to monitor and continually improve the methods used by friction ridge identification specialists. Implementing a friction ridge identification methodology and philosophy that is accepted and used by the identifcation community throughout the world will certainly assist in emphasizing the scientific basis on which friction ridge identification is founded. As mentioned earlier, in depth study of the anatomy and growth of friction skin is crucial before attempting to understand how a friction ridge identification specialist can apply any methodology and philosophy and in the end come to the conclusion that an impression of a very small area of friction ridge skin came from one source and one source only. I have attempted to give you some insight into the Anatomy of Friction Skin and Growth of Friction Skin on other pages found on this web site. The Friction Ridge Identification Process incorporates a scientific methodology and an identification philosophy. The methodology is "a structured and systematic manner in which quantitative-qualitative analysis of friction ridges is carried out". (Quantitative-Qualitative Friction Ridge Analysis, Introduction to Basic Ridgeology, May 1999, pg.75) Understanding the identification philosophy is only accomplished by first learning about the premises of friction skin identification and how scientific research in anatomy, biology, histology, embryology etc. has supported these premises...primarily the uniqueness and permanency of friction skin. The identification philosophy can best be paraphrased by the following statement: "Friction ridge identification is established through the agreement of friction ridge formations, in sequence, having sufficient [observed] uniqueness to establish individuality."
"Ridgeology", a term coined by David Ashbaugh in an article published in 1983, in my opinion, puts it all together. Ridgeology is defined as "The study of the uniqueness of friction ridge structures and their use for personal identification". (Quantitatve-Qualitative Friction Ridge Analysis, Introduction to Basic Ridgeology, May 1999, pg.8)