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United States v. Cazares, 788 F.3d 956 (9th Cir. 2015)

Case (cite)
United States v. Cazares, 788 F.3d 956 (9th Cir. 2015)
Type of proceeding
Type of claim
Type of claim (second claim)
Expert evidence ruling reversing or affirming on appeal:
What was the ruling?
No Error due to Harmless Error
Type of evidence at issue:
Firearms identification
Defense or Prosecution Expert
Name of expert(s) who were the subject of the ruling
Diana Paul
Summary of reasons for ruling
The defendant argues that the expert should not have been allowed to testify to "scientific certainty." The court held that, although the testimony to scientific certainty was important, it was subject to extensive cross-examination which acknoweldged the subjectivity involved in firearms indentification. The court holds that "a reasonable degree of certainty in the ballistics field" is the proper testimony but that "scientific certainty" was harmless error.
The jurisdiction’s standard for expert admissibility at the time – list all that apply: (Frye), (Daubert), (Post-2000 Rule 702), (Other)
Second standard
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).
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)
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


Even the government is not arguing on appeal that “scientific certainty” is a proper characterization for toolmark identification expert testimony. While there may be some deficiency in the objections to the standard testified to by Paul, it appears that the “scientific certainty” issue was brought to the district court’s attention before and during Paul’s testimony. A more thorough Daubert hearing could have been helpful in handling the “scientific certainty” issue. The issue is then whether the “scientific certainty” characterization was harmless error.
48 An error is harmless unless it results in actual prejudice, which is demonstrated where “the error in question had a ‘substantial and injurious effect or influence in determining the jury’s verdict.’ ” Winzer, 494 F.3d at 1201 (quoting Brecht, 507 U.S. at 623, 113 S.Ct. 1710). Although the firearms identification evidence and expert testimony was important in this case, the “scientific certainty” characterization was subject to cross examination which resulted in acknowledgment of subjectivity in the expert’s work. In addition, the district court properly instructed as to the role of expert testimony and there was substantial evidence otherwise linking the defendants to the Wilson and Bowser murders. We believe “a reasonable degree of certainty in the ballistics field” is the proper expert characterization of toolmark identification. Any error in this case from the “scientific certainty” characterization was harmless.