Reliability of Fingerprinting Evidence
As a general proposition, fingerprint experts believe that fingerprint patterns never change and are unique to each individual. For this reason, state and federal judges do not usually question their evidentiary validity. Juries typically agree when such evidence suggests an individual is guilty of committing a crime. At times, such evidence is so convincing that individuals accused of crimes confess when confronted with a “match.”
Despite the widespread acceptance of fingerprint evidence, many question its worth due to a significant amount of identification mistakes. For example, in 2000, an individual was arrested for murder and was told by police that fingerprint experts matched his fingerprints to those found at the crime scene. The individual’s attorney hired his own fingerprint experts, two former FBI examiners, who determined that absolutely no positive identification took place. After some post-incarceration legal wrangling, this evidence was deemed sufficient for an acquittal.
Lack of Uniform Standards for Fingerprint Analysis
Mistakes in identification may occur because the actual determination of a match is based on human inspection, a process many deem to be an imperfect science. In fact, the International Association for Identification (IAI), an organization considered by many experts as the authority for fingerprint analysis certification, determined in 1973 that there is no need to require a set formula or standard in order to prove a fingerprint match. Specifically, it stated that “no valid basis exists to require a predetermined number of characteristics to exist between two fingerprint impressions in order to establish positive identity.”
The Scientific Working Group on Friction Ridge Analysis, Study, and Technology (SWGFAST), another recognized fingerprint organization, sets forth standards to assure quality fingerprint examination. However, for fingerprint professionals, the SWGFAST standards are merely optional guidelines. Similarly, approximately 50% of the examiners who take the IAI test fail the exam, but are still permitted to work since there is no requirement that such professionals be certified.
Thus, there is no uniform definition of a match, and many states disagree on how many points of similarity are needed before declaring the existence of a match.
Federal Court Questions Validity of Fingerprint Evidence
In early 2002, a federal judge handed down a ruling, albeit temporary, that sent ripples through the legal community regarding the reliability of fingerprint evidence. In United States vs. Llera Plaza, the court ruled that according to standards established by the U.S. Supreme Court regarding the admissibility of expert scientific testimony, the use of fingerprint expert testimony should be limited.
In Llera Plaza, the court tested the reliability and usefulness of fingerprint evidence against the standards set out by the U.S. Supreme Court’s 1993 landmark decision in Daubert v. Merrel Dow Pharmaceuticals. In Daubert, the Court set forth a four-prong test to determine whether scientific evidence is relevant and reliable, i.e., “based on scientific knowledge”:
- Whether the technique can be (and has been) tested
- Whether the technique has been subjected to peer review and publication
- The known or potential rate of error…and the existence and maintenance of standards controlling the technique’s operation
- General acceptance
Applying the Daubert test, the Llera Plaza court initially ruled that such evidence did not satisfy most of the factors and, therefore, was not scientifically reliable. However, in response to a motion by the prosecution to reconsider the ruling, the court heard additional testimony from “leading experts” that persuaded the court that the methodology behind fingerprint testing was indeed “tested” and “generally accepted.” Consequently, the court reversed the previous ruling and allowed expert opinion testimony regarding the likelihood of fingerprint matches.
Every federal court that has considered expert fingerprint identification has upheld the admissibility of such evidence.