If there is one form of evidence that sticks most with people when they are asked to start listing the things that police see as clues in an investigation, it's probably the presence of fingerprints. For younger people, there's a solid chance that the answer could also be DNA, but for anyone who remembers the days before DNA testing, fingerprinting is quick to spring to the front of the mind and the tip of the tongue.
Even as DNA evidence has gained support, and the sophistication of testing methods and processes has grown, fingerprint evidence remains an important part of police investigations in the United States and around the world. Despite this fact, though, the research into fingerprinting has some surprising holes.
The practice of fingerprint matching relies on one particular assumption, and without it, the entire field falls apart. That assumption is that every individual has unique fingerprints and that prints do not repeat. There's just one problem with that: there are no peer-reviewed studies substantiating this as fact in the National Academy of Sciences database. At all. PBS's Frontline detailed this and other issues with forensic evidence in a 2012 article.
There are a variety of other reasons why fingerprint evidence fails to make the grade as scientific proof, but the inability to determine for a fact that fingerprints are unique undermines the entire basis of the practice as evidence. Those other issues include:
- The evidence is affected by contextual bias, meaning the determinations can change based on a researcher's implicit beliefs and biases.
- The number of points of identification needed to make a match vary from state to state with little discernible reason.
- Fingerprint analysis was not developed by scientists using a scientific methodology, but by police and police investigators, and it has not been investigated scientifically.
That last point is the most important one of all. The New Yorker explains in a comprehensive history of the practice how police investigators first began using the techniques in the 19th century, how they developed over time, and how modern computer tools help to make substantiating matches more reliable. None of those things make it scientific, however. To be scientific, it has to be subjected to the kind of error-checking and analysis that science employs to be sure of its findings.
If you are facing any kind of criminal charges and are worried about the way fingerprint evidence might have been handled in your case, you need to talk to a criminal defense attorney. The best defense is to avoid the situations and people who might place you at a scene, but if that just cannot happen for whatever reason, experienced help is your next step.