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United States. v. Glynn, 578 F.Supp.2d 567 (S.D.N.Y. 2008)

Case (cite)
United States. v. Glynn, 578 F.Supp.2d 567 (S.D.N.Y. 2008)
Type of proceeding
Type of claim
Type of claim (second claim)
Expert evidence ruling reversing or affirming on appeal:
What was the ruling?
Type of evidence at issue:
Firearms identification
Defense or Prosecution Expert
Name of expert(s) who were the subject of the ruling
Detective James Valenti
Summary of reasons for ruling
limit the expert's testimony from “to a reasonable degree of ballistic certainty” to "more likely than not" - because (1) ballistics forensics is too subjective to be science ("sufficient agreement" is a vague concept); (2) "to a reasonable degree of ballistic certainty" would "seriously mislead the jury as to the nature of the expertise involved"; (3) but since it has gathered "sufficient support as to warrant its admissibility" - it is still admissible but has to be qualified.
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).
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)
All factors
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


“Firearm and toolmark analysis rests on the twin assumptions that the surface contours of every gun are unique and that, every time that gun is fired, some of those unique markings, along with markings caused by the fact of firing itself, are transferred to the shell casing and bullet, leaving distinctive patterns on each of them.”




“[F]or many decades ballistics testimony was accepted almost without question in most federal courts in the United States . . . But like many other forms of expert testimony, this practice was subjected to new scrutiny in light of Daubert and Kumho Tire and the subsequent amendment to FRE 702, which gave to the courts a more significant gatekeeper role with respect to the admissibility of scientific and technical evidence than courts previously had played.”


“[T]he ballistics comparison lacks defining standards to a degree that exceeds mos other kinds of forensic expertise.” (there is no general agreement on how many points would make a sufficent match)


on the limitations of cross-examinination process: “Although effective cross-examination may mitigate some of these dangers, the explicit premise of Daubert and Kumho Tire is that, when it comes to expert testimony, cross-examination is inherently handicapped by the jury’s own lack of background knowledge, so taht the Court must play a greater role, not only in excluding unreliable testimony, but also in alerting the jury to the limitations of what is presented.”


It follows that ballistics examination not only lacks the rigor of science but suffers from greater uncertainty than many other kinds of forensic evidence. Yet its methodology has garnered sufficient empirical support as to warrant its admissibility.


On the degree of confidence: “This latter issue is particularly important because, once expert testimony is admitted into evidence, juries are required to evaluate the expert’s testimony and decide what weight to accord it, but are necessarily handicapped in doing so by their own lack of expertise. There is therefore is a special need in such circumstances for the Court, if it admits such testimony at all, to limit the degree of confidence which the expert is reasonably permitted to espouse.”