Skip to content

U.S. v. Brown, 973 F.3d 667 (7th Cir. 2020)

Case (cite)
U.S. v. Brown, 973 F.3d 667 (7th Cir. 2020)
Type of proceeding
Type of claim
Type of claim (second claim)
Expert evidence ruling reversing or affirming on appeal:
What was the ruling?
Correct to Admit
Type of evidence at issue:
Firearms identification
Defense or Prosecution Expert
Name of expert(s) who were the subject of the ruling
Marc Pomerance; Kury Murray; Aimee Stevens; Rodney Jiggets
Summary of reasons for ruling
Defendants challenged the reliability of the AFTE method and toolmark identification broadly and relied on the PCAST report to support their argument. The court held that the trial court did not abuse its discretion in admitting the expert testimony. The reasoned that the AFTE method had been subject to peer review, was widely accepted by courts, and that although error rates vary, they are generally very low. Any issues the defense had with the methods could be raised on cross and would go to the weight of the testimony, not the admissibility.
The jurisdiction’s standard for expert admissibility at the time – list all that apply: (Frye), (Daubert), (Post-2000 Rule 702), (Other)
Second standard
Rule 702
Did lower court hold a hearing
Names of prosecution expert(s) two testified at hearing
Names of defense expert(s) who testified at hearing (or None).
William Tobin (at trial, not hearing)
Discussion of 2009 NAS Report (NAS2009)
Discussion of 2016 PCAST report (PCAST)
Discussion of error rates / reliability
Frye Ruling
Limiting testimony ruling
Language imposed by court to limit testimony
Ruling based in prior precedent / judicial notice
Daubert ruling emphasizing – which factors – (list 1-5)
(1); (2); (3); (5)
Ruling on qualifications of expert
Ruling on 702(a) – the expert will help / assist the jury
Ruling on 702(b) – the testimony is based on sufficient facts or data
Ruling on 702(c) – the testimony is the product of reliable principles and methods
Ruling on 702(d) – reliable application of principles and methods to the facts of the case


“Taking these criteria into account, the district court found the toolmark evidence was admissible. It noted that the Association of Firearms and Toolmark Examiners (AFTE) methodology used by the government’s witnesses had been “almost uniformly accepted by federal courts.” See, e.g., Cazares, 788 F.3d at 989. The AFTE method has been tested and subjected to peer review. Three different peer-reviewed journals address the AFTE method, and several reliability studies have been conducted on it. Although the error rate of this method varies slightly from study to study, overall it is low—in the single digits—and as the district court observed, sometimes better than algorithms developed by scientists. The court also noted that firearm and toolmark analysis is widely accepted beyond the judicial system.”