Special Action from the Superior Court in Maricopa County. The Honorable Jerry Bernstein, Judge Pro Tempore. No. CR2010-126778. Opinion of the Court of Appeals, Division One, 234 Ariz. 89, 317 P.3d 630 (App. 2014) .
Special Action from the Superior Court in Maricopa County, VACATED AND REMANDED. Opinion of the Court of Appeals, Division One, VACATED IN PART.
W. Clifford Girard, Jr., Mark D. DuBiel, Lawrence Koplow, Joseph P. St. Louis (argued), Phoenix, Attorneys for Doreen Lynn Herman, et al.
William G. Montgomery, Maricopa County Attorney, Lisa Marie Martin (argued), Deputy County Attorney, Phoenix, Attorneys for State of Arizona.
Bruce Washburn, Scottsdale City Attorney, Ken Flint, Assistant City Prosecutor, Scottsdale, Attorneys for Amicus Curiae City of Scottsdale.
Alan B. Kelly, Scottsdale, Attorney for Amicus Curiae Scottsdale Lincoln Health Network.
CHIEF JUSTICE BALES authored the opinion of the Court, in which VICE CHIEF JUSTICE PELANDER, and JUSTICES BERCH, BRUTINEL, and TIMMER joined.
BALES, CHIEF JUSTICE:
¶1 Arizona Rule of Evidence 702 requires a trial court to act as a gatekeeper to ensure that only reliable expert witness testimony is admitted for the jury's consideration. This case concerns the trial court's role under Rule 702(d) when a party contends that an expert has not properly applied generally reliable principles or methods. We hold that courts, as gatekeepers, should consider whether a methodology has been correctly applied. But we conclude that errors in application should result in the exclusion of evidence only if they render the expert's conclusions unreliable; otherwise, the jury should be allowed to consider whether the expert properly applied the methodology in determining the weight or credibility of the expert testimony.
¶2 Real parties in interest are eleven defendants charged with aggravated driving under the influence. The Scottsdale Crime Laboratory (" SCL" ) tested each defendant's blood for blood alcohol concentration (" BAC" ). As described by the court of appeals:
To test the blood, the SCL used a Clarus 500 gas chromatograph serial number 650N9042003 manufactured by PerkinElmer (the 2003 Instrument), an autosampler, a personal computer and a printer. Stated simply, after calibration, several dozen vials are placed in the carousel of the 2003 Instrument. The vials contain blood samples (each individual has two samples tested at a time, with the second sample called a replicate) along with control samples. The vials are sampled, one by one, and analyzed by the 2003 Instrument, a process that takes several hours. The data are then processed (creating graphs showing the chemical properties of
the compounds tested for called chromatograms) and results are calculated and printed. The output is checked for consistency with expected results, control samples and quality controls, and replicates are checked to make sure that results are within plus or minus five percent of each other according to SCL protocol. A second ...