State v. Langlois, 2 N.E.3d 936 (Ohio Ct. App 2013)

on error rate: “While acknowledging that the results of such tests do not have an established potential rate of error, hetestified that numerous studies have confirmed the accuracy of the techniques that formed the basis for his conclusions. He cited one study conducted over a ten year period that involved over 500 firearms examiners. Consecutively manufactuered firearms barrels were examined for distinguishing tool marks left on projectiles and ‘7500 correct conclusions’ were reached. ‘There was no false positives,’ he stated, ‘which means no one accidentally attributed a projectile to the wrong barrel.’ . . . similar studies analyzing the markings on fired shell cases have been published as well”

“Notably, [the defendant] offered no contrary testimony to refute the state’s ballistics experts. . . . He presented no credibloe challenge to the underlying physical or scientifictheory of how marks are transferred from a firearm to the primary components of a cartridge, nor to the methodology of identifying a match betwwen a particular gun and a shell case found at the crime scene.”

on reliability: Both experts used widely-accepted and accurate microscopic methods for observing minute striations and primer cup indentations on the cases being examined. . . . Such microscopic comparison testing is a generally accepted method of forensic analysis. . . .Our conclusion on this issue finds support in the decisions of other appellate districts in Ohio, notwithstanding the recent criticisms in scientific reports and the limitations some federal courts have imposed on th testimony of firearms experts. These decisions hold taht the methodology of comparatively analyzing and testing bullets and shell cases revovered from crime scenes is reliable.