State of Arizona v. Joseph Javier Romero, 365 P.3d 358

Background

In June 2000 a man was shot; police recovered six spent .40-caliber shell casings at the scene and later recovered a .40-caliber Glock and magazine near Romero after a 2000 stop. Years later a cold-case investigation linked the phone found at the scene to Romero.
Firearms examiner Frank Powell testified that the six casings were fired from the same gun and that test-firing the recovered Glock produced matching toolmarks; he testified to a match to a “reasonable degree of scientific certainty.”
Romero was retried after a mistrial; before retrial he moved to exclude Powell under Ariz. R. Evid. 702/Daubert and proffered Dr. Ralph Haber, an expert in experimental design, to testify criticizing the scientific reliability of toolmark comparisons.
The trial court admitted Powell but excluded Dr. Haber, finding Haber unqualified in firearms identification and that allowing him would improperly require the jury to revisit the court’s Daubert gatekeeping ruling.
On appeal the court of appeals affirmed exclusion (divided panel); this Court granted review limited to whether excluding Dr. Haber was error under Rule 702.
The Arizona Supreme Court held Dr. Haber was qualified to testify about experimental design, his testimony would be helpful to the jury, and exclusion on the ground it would amount to a second Daubert hearing was erroneous; remanded to determine whether the error was harmless.

Issues

Issue	Romero's Argument	State's Argument	Held
Whether the trial court properly excluded Dr. Haber under Rule 702	Haber is qualified in experimental design and may explain how toolmark methods differ from scientific experimental methods; admissible to help jury assess weight	Haber is not qualified in firearms identification; his testimony would invite re-litigation of the court’s pretrial Daubert ruling	Court: Haber is qualified to testify about experimental design; exclusion for lack of firearms credentials was error
Whether expertise must be in same specialty as opposing expert	No — opposing expert may be qualified in a different but relevant discipline (experimental design) to critique methods	Expert must be a firearms/toolmark examiner to critique examiner's methods	Court: Rule 702 permits qualification via knowledge, training, experience; different relevant expertise is acceptable
Whether Haber’s testimony would be helpful to the jury (Rule 702(a))	His critique of toolmark methodology and lack of standardized protocols would help jurors weigh Powell’s “scientific” certainty	Haber hadn’t performed toolmark analyses and couldn’t describe specific protocols; therefore not helpful	Court: Testimony would be helpful; lack of hands-on experience goes to weight, not admissibility
Whether admitting State expert precludes defense from presenting contrary expert at trial (i.e., forbids a “second Daubert” before jury)	Defense may present contrary expert evidence at trial to challenge weight/credibility even if court previously admitted State expert	Allowing defense expert would improperly relitigate the court’s admissibility ruling	Court: Precluding defense expert on that basis is error; jurors decide weight and credibility; Lehr and Rule 702 support allowing such evidence

Key Cases Cited

Daubert v. Merrell Dow Pharm., 509 U.S. 579 (gatekeeping standard for admissibility of scientific expert testimony)
State v. Lehr, 201 Ariz. 509 (trial court erred by blocking trial challenge to admissible expert; weight and credibility for jury)
State v. Bernstein, 237 Ariz. 226 (interpretation of Rule 702; close questions of reliability go to jury)
State v. Salazar-Mercado, 234 Ariz. 590 (admitting general expert testimony to assist jury; "cold" expert testimony admissible)
State v. Girdler, 138 Ariz. 482 (standard for qualifying expert: knowledge superior to laypersons)
State v. Macumber, 112 Ariz. 569 (careful study may suffice to qualify an expert)
State v. Watson, 114 Ariz. 1 (expert qualification principles)