Although evidence supports the uncertainty and unreliability of fingerprint evidence in criminal cases, it is still reliable in identifying suspects

A fingerprint is an impression of the friction ridges of the finger. There are sweat glands in the skin of a finger that produces a solution that coats the ridges of the prints. When one touches a surface the residue is left with the pattern of ones fingers. This residue left on a surface is called a latent print.
A latent print is different from a suspect print in that a latent print is the print found at a crime scene while a suspect print is one collected from a suspect for matching purposes.
In identifying and lifting latent prints, fingerprint dust has to be used to dust the surface and adhesive tape is used to lift that print. A common misconception is that this process is foolproof but it is not. For example, if the latent  print is on a moist surface, then dusting the surface will distort the print.


A study has found that there is a 0.1 false positive error rate and 7.5 false negative error rate

In a research conducted by the National Research Council of the National Academies, researchers sought to measure the accuracy and reliability of latent print examiners' decisions such as the ones in the Brandon Mayfield Case. In this study, 169 latent print examiners each compared approximately 100 pairs  of latent and exemplar fingerprints. The results of the study are very significant. 3 percent of the examiners made at least one false positive error for an overall rate of 0.1 percent. False positive means that the examiner stated that the latent print and the exemplar matched when in fact they do not match. 85 percent of the examiners made at least one false negative error for an overall rate of 7.5 percent. False negative means that the examiner stated that the latent print and the exemplar do not match when in fact they do.
When asked whether or not he thought that the results of this study represents the error rate in the fingerprint community, Professor of Criminalistics at the University of Maryland, Tom Mauriello stated that matching fingerprints is an art and not a science so an error rate is expected. He states, "If it was science, then we would have to give the correct answer every time" and because of this, we have to expect mistakes to be made.
















With the error rates cited in a study, it is not enough for fingerprint evidence to be rejected in courts
When asked whether or not the error rates were high enough to be concerning to the forensic field, Professor Mauriello said no. Specifically, when asked about the false negative errors in which the examiners stated conclusively that the fingerprints do not match when in fact they do, Mauriello states, "No one piece of evidence should be the deciding factor between finding a defendant guilty or not guilty."





Brandon Mayfield was one of the people affected by the 0.1 percent false positive error rate and the result was devastating

March 11, 2004, ten bombs were detonated in Madrid, Spain. 193 people died and 1,800 people were injured. One of the bombs, however did not detonate. The bombs were contained in backpacks, gym bags and other small bags. Partial fingerprints were found on the bag with the undetonated bomb. The
Spanish Police found two partial fingerprints that were later send to the Federal Bureau of Investigation (FBI) for identification.
The FBI ran the prints through the Automated Fingerprint Identification System (AFIS) and twenty matches came up for the prints. Although AFIS identifies several identical fingerprints, the final decision is ultimately based on the examiner. Five fingerprint examiners examined the prints and came up with a match. Brandon Mayfield, a United States citizen was one of the twenty matches that came up through AFIS. This was a highly publicized case because of the casualties in the bombings.

In order to reduce the error rates or prevent something like the Mayfield case from happening again, Professor Mauriello advises that the fingerprint community should establish standards. Mauriello also states that the Mayfield case was the result of political pressure on the FBI. They were pressured to make a match. They let their bias get in the way of the truth. He states, "If you let your bias interfere with your judgement, you will make those kinds of mistake."

The way to prevent this bias is blind quality control. The person who overlooks the result should have no knowledge of the case. Brandon Mayfield was never charged for the crime he was accused of committing. He was eventually released because the Spanish Authorities matched the fingerprints to a known terrorist in Spain.