It would be farcical to preclude experienced ballistics experts from rendering any opinion about known manufacturing marks. There is a consensus, or at least not all that much disagreement, to allow examiners to express an opinion on toolmarks that are class characteristics. The defendants’ challenge to all expert testimony on toolmarks is therefore rejected.
Courts must be wary when scientific evidence is offered to prove a defendant’s guilt. The problem of a microscopist putting expert conclusions before the jury is not solved by the opportunity to cross examine or present a countervailing expert on methodology. Experts enter upon the jury’s province, since the expert—and not the jury—draws conclusions from the facts. . . . The testimony of “sufficient agreement of a match” or even the language “consistent with” goes to the heart of the question of guilt.
Fortunately, evidence submitted at the hearing suggests positive change is coming. Research into 3D technology promises a potential for automatic analysis of the surface topographies of bullets, such that the current problems of subjectivity and quantifying the marks and impressions more precisely. (People’s Ex. 31, 36). As Dr. Hofmann observed, “[m]atching bullets is clearly not a one-step process, but rather a sequence of data analysis tasks each deserving attention. As there is no scientific standard in place at this point in time, our intent is to explain an approach to addressing these tasks, *918 while documenting all steps and providing all code so that other researchers and forensic scientists can reproduce and expand on our findings. Science may well eliminate the interpretation, guesswork and biases associated with visual forensic examinations.”
“Forensic scientists maintain that by examining toolmarks under a microscope, a trained examiner can determine whether there is “sufficient” agreement to reliably identify a particular *902 firearm as the source of the toolmarks. Researchers in traditional scientific disciplines– including study design and research methodology, statistics and psychology–are unified in their view that toolmark identification is just a practice in search of a science and is not reliable.”
“As a number of courts have pointed out that the AFTE standard is circular—an identification can be made upon sufficient agreement, and agreement is sufficient when an identification can be made.”
Relevant scienfic community: “The People adhere to the view that the relevant scientific community should be limited to forensic scientists and their established conclusions. Yet Frye demands an unbiased, objective review by those with no professional interest in its acceptance. . . . The professional standing and livelihood of forensic scientists depends on the validity of AFTE theory. See United States v. Tibbs, 2019 D.C. Super. LEXIS 9. Certainly this came across in the testimony of Mr. Weller, a professional consultant and frequent expert witness for the prosecution. The targeted use of AFTE theory by law enforcement investigators, under pressure and with potential for confirmation bias, limits the degree of intellectual rigor and detachment that counts as neutral scientific expertise.”
Most courts conclude that although the studies have flaws and the error rates are simply too hard to calculate, because of the rigor of examiner training and the assumption that error rates are low, some expert toolmark testimony should be permitted. See United States v. Johnson, 2019 WL 1130258. But a number of district courts hearing Daubert17 challenges have broadened the relevant **640 scientific community to take into account the contrasting views of mainstream researchers. Consequently, the scope of permissible expert toolmark testimony is narrowing overall.
Forensic scientists and AFTE themselves have not taken a head-in-the-sand attitude lately but appeared to recognize that toolmark identification, while time honored in the field and the courtroom, is under attack and must withstand scrutiny by other researchers. The People submitted numerous exhibits demonstrating that forensic science has picked up the pace and virtually raced to publish favorable studies. Where forensic science has fallen short, however, is that these validation efforts have been afflicted by fatally flawed study designs and subpar quantitative and qualitative measurements.