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Is Forensic Testimony Reliable? Not Always.

The Consequences of Inconclusiveness

Juries who are told that forensic experts are 100% reliable should be cautious. Oftentimes, forensic testimony is not questioned in criminal trials because these experts are perceived as accurate and truthful no matter what. After all, they’re experts, right?

However, a paper by Itiel Dror and Nicholas Scurich, “(Mis)use of Scientific Measurements in Forensic Science,” examines a significant issue in the validation of firearm and fingerprint comparisons by forensic experts. In these instances, “validated” refers to how forensic disciplines are tested for their reliability and likelihood of producing flawed results, according to a Slate article by Daniel Epstein and David Epstein.

While it may seem straightforward for experts to identify matches and nonmatches between fingerprints and shell casings ejected from guns, the reality is, the scoring system used to confirm the accuracy of their results can do more harm than good.

Let’s take a closer look.

An Unreliable System Used to Test Reliability

When forensic experts are tested to determine if they can identify matches from nonmatches in firearms and fingerprinting matters, they are given the freedom to confirm or deny a match or simply state their findings are “inconclusive.” The scoring system used to test these experts does not consider “inconclusive” findings as incorrect, therefore, a forensic expert who answers “inconclusive” on all questions in a 10-question test will receive a 100% score.

If, however, an expert wrongfully confirms a match but answers “inconclusive” on all other questions in the 10-question test, they will receive a 90% score. An expert can “cheat the system” by choosing the easiest question on a test and answering it correctly, but writing “inconclusive” for the remaining questions to receive a 100% score.

As a result, you must question the accuracy and reliability of forensic testimony, no matter how trustworthy it may seem.

In their paper, Dror and Scurich described a study in which experts were tested on the same fingerprints 7 months apart. 10% of the time, the same expert reached a different conclusion about the same fingerprint that they had examined 7 months ago. Another study involved firearm forensics experts examining the same shell casings but reaching different conclusions. One expert confirmed that a shell matched the gun while another said it was “inconclusive.” Now that you know “inconclusive” isn’t deemed incorrect, you may not be surprised that the study reported a 0% error rate despite the experts reaching different conclusions about the same shell casings.

So, how does this error impact criminal cases? In criminal trials, the difference between confirming or denying that a fingerprint rules out a defendant and saying that their fingerprints are inconclusive can mean the difference between freedom and a conviction.

To put it into perspective, an FBI firearms examiner conducted a study in which forensic experts were told that they were “participating in a blind validation study, and that an incorrect response could adversely affect the theory of firearms identification.” As a result, these experts were inherently encouraged to choose “inconclusive” to protect the reputation of their field in legal cases.

Imagine if you were a math teacher told to take a math test, and your students could access your results online. Your reputation and credibility would be at stake, as a bad test score may cause your students to question your authority and lose trust in you or the institution that you work for. As such, if you were told that writing “unsure” wouldn’t be counted as incorrect, you would feel incentivized to select that answer in order to achieve a 100% score on the test.

This is the position that forensic examiners are often placed in, therefore your criminal defense lawyer must challenge every element of their testimonies to ensure they are 100% accurate. Your freedom and future depend on it.

Questions? Come Talk to Us.

With all of the above information in mind, you should discuss your situation with our award-winning Las Vegas criminal defense attorney at the Law Office of David R. Fischer. We understand that experts are not entirely reliable and may produce questionable results that could impact the outcome of your case, which is why we will go above and beyond to scrutinize every element of the prosecution’s case against you. With a reputation for achieving favorable outcomes for clients, you can count on us to fight for what you deserve no matter what you’re up against.

Contact us at today. To access the full Slate article by Daniel Epstein and David Epstein, please click here.