Over the past several weeks we’ve reviewed various different types of evidence. Last week, we examined one particular example of evidence: polygraph tests. We cast doubt on their validity. This week we’ll look at fingerprints. Every crime show seems to place a great deal of emphasis on fingerprints. But are fingerprints reliable evidence? What do they prove, if anything?

Why Do People Think Fingerprints Are Reliable Evidence?

First, why have people put so much weight on fingerprints in the past? One of the earliest examples of using fingerprints to solve crimes was by Henry Faulds, a Scottish physician and missionary to Japan in the late 1800s. He caught a hospital employee stealing alcohol by matching the fingerprints from a test paper to a glass beaker. People began to trust fingerprint evidence more and more because…

• Once you become an adult, your fingerprint does not drastically change over time.
• A fingerprint can stay on a well-preserved surface for years.
• Fingerprints seemed unique to each person.
• The oils on your skin make it very easy to leave fingerprints anywhere.
• Fingerprint patterns seem easy to match.

From these details and assumptions, Qazi Azizul Haque and Edward Henry developed ways of classifying fingerprints. Their methods remained influential from the 1890s all the way through to the 1990s.

Are Fingerprints Reliable Evidence?

Second, now that we understand why people have taken fingerprints seriously, we have to raise certain questions. Are the five points listed above really true? The real problems arise with the last three points.

According to one source, 1 in 64 trillion people have the same fingerprint. But this is from 1894! We lack enough modern research to support such a claim. Next, it is easy to leave fingerprints on surfaces. However, it is not easy to leave detailed, clear, clean fingerprints on surfaces. One little motion and the fingerprint left will be imperfect. For that reason, we cannot match them as easily as some might think. Furthermore, an imperfect fingerprint casts doubt on all the other facets that would otherwise make it reliable. How many points of similarity between two prints make them a “match”? Five? Ten? Can we really make accurate matches without perfect prints?

As one forensic scientist has said, “the uniqueness of fingerprints and the accuracy of fingerprint identification are two completely different questions.” In a 2017 study by the American Association for the Advancement of Science, criminologist William Thompson argued, “We have concluded that latent print examiners should avoid claiming that they can associate a latent print with a single source and should particularly avoid claiming or implying that they can do so infallibly, with 100% accuracy.”

You Need Attorney Mark Catanzaro!

Finally, are fingerprints reliable evidence? We doubt it. And so should the jury. So don’t let fingerprint evidence in your trial ruin your case! If you want an attorney who will help the jury see the truth, contact Mark Catanzaro today!