EvidenceProf Blog

Editor: Colin Miller
Univ. of South Carolina School of Law

Tuesday, June 22, 2021

Court Circumscribes Firearm Toolmark Testimony in Murder Trial

With firemark toolmark testimony, a ballistics expert testifies that a particular shell casing came from a particular gun. Here is how we described it in our recent Undisclosed series about the Darrell Ewing trial:

When Derrico Searcy was arrested for his role in the murder, he was in a blue BMW that was registered to a man named Garland Royal. Police Officer Lori Dillon was one of the officers completing the arrest, and while searching the BMW, she recovered three 9 millimeter shell casings from the bottom of the windshield near the wiper blades. 

Those casings and casings recovered from the crime scene were sent to Robert Charlton, a toolmark examiner with the Oakland County Sheriff’s Office. Charlton’s job sounds simple: determining whether the casings from the BMW and the casings from the crime scene came from the same gun. Of course, as we noted in Episode 1 and as Charlton acknowledged in his testimony, no gun was recovered in this case, meaning he couldn’t fire a third set of bullets and compare the markings on their casings to the markings on the two other sets of casings.

But what he did sounds pretty scientific. For example, here’s one Q&A from his testimony:

Screen Shot 2021-06-22 at 10.05.12 AM


Sounds pretty cool, right? Well, it’s not. It’s junk science. In 2016, the Executive Office of the President President’s Council of Advisors on Science and Technology, or PCAST, issued a report to the President. The report noted that:

In firearms analysis, examiners attempt to determine whether ammunition is or is not associated with a specific firearm based on “toolmarks” produced by guns on the ammunition….

Firearms analysts have long stated that their discipline has near-perfect accuracy; however, the 2009 National Research Council study of all the forensic disciplines concluded about firearms analysis that “sufficient studies have not been done to understand the reliability and reproducibility of the methods”—that is, that the foundational validity of the field had not been established. 

Our own extensive review of the relevant literature prior to 2009 is consistent with the National Research Council’s conclusion. We find that many of these earlier studies were inappropriately designed to assess foundational validity and estimate reliability. Indeed, there is internal evidence among the studies themselves indicating that many previous studies underestimated the false positive rate by at least 100-fold

And while the report held that the foundational admissibility of firearm toolmark testimony was a question for the courts, it left no question about the foundational validity of such evidence. According to PCAST, “the current evidence still falls short of the scientific criteria for foundational validity.”

In other words, if Darrell Ewing were being tried in 2021, he would have a lot of ammunition for the argument that firearm toolmark evidence should be deemed inadmissible or at least taken with a huge grain of salt.

Well, as of yesterday, it looks like Darrell Ewing will have that new trial in 2021. And, in terms of ammunition, the Davis Vanguard reports on exactly how that might look. A recent article reports on a ruling about firearm toolmark testimony in the case of Tuala Auimatagi, who is charged with the murders of Errik Sanchez and Bruce Wayne Allen. Based on the defense arguing that such testimony is unreliable, the judge ruled as follows:

The judge will permit him to “describe the class characteristics he observed on the bullets” and “[t]he theory of toolmark analysis and how firearms leave markings on bullets or shell casing.”

He will also be allowed “to testify that he cannot exclude or eliminate the bullets as coming from different guns.”

However, “[H]e will not be permitted to describe any greater level of scientific certainty than the bullets may or may not have come from the same gun.”



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It's great Ewing is going to get a new trial, and I'm glad the court isn't just letting the junk scientist spout whatever he wants, but what probative or evidentiary value is there in letting this "expert" testify at all?

Posted by: bacchys | Jun 22, 2021 12:34:24 PM

Given that "However, “[H]e will not be permitted to describe any greater level of scientific certainty than the bullets may or may not have come from the same gun.” ... What is the point of having him testify? Such statements ('may or may not') do not appear to add any evidentiary value one way or the other.

Posted by: Sadie Sullivan-Greiner | Jul 14, 2021 3:58:23 PM

I disagree. It is relevant that the defendant's gun cannot be eliminated from being "the gun." = "any tendency" to prove a fact. Also, the absence of the expert's testimony leaves open the chance the jury will conclude there is no evidence that the defendant's gun could be "the gun." Finally, the jury would be left wondering why the state did not test the bullets or shells for striations. This is valuable "gap-filling."

Posted by: Fred Moss | Jul 19, 2021 2:42:24 PM

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