2/4/16 Arizona Rules of Evidence, Rule 702 allows an expert witness to testify if, among other things, the witness is qualified and the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence. Trial courts serve as the “gatekeepers” of admissibility for expert testimony, with the aim of ensuring such testimony is reliable and helpful to the jury. On January 20, 2016, in State v. Romero, The Arizona Supreme Court held that a trial court had improperly prohibited a defendant from having an expert testify at the jury trial and offer testimony questioning the State’s firearms expert. At trial the State’s expert testified that his conclusion was, to a scientific certainty, that marks on shell casings found at a murder scene came from one gun. The trial court prohibited the defense expert from testifying to contradict that conclusion because the defense witness was not a firearms expert. The Supreme Court ruled that the defense expert was familiar with the underlying testing procedures used to come to the type of conclusion the State’s expert came to, and with that knowledge the defense expert could have said that the underlying principles used by the State’s expert were not scientifically reliable. The Supreme Court said the defense expert’s testimony would have been able to impeach the State’s witness’s testimony and therefore should have been admitted at the trial. The Supreme Court then sent the case back to the Court of Appeals to see if admitting the defense expert’s testimony would make a difference in the outcome of the trial. Below is a link to the case:
http://www.azcourts.gov/Portals/0/OpinionFiles/Supreme/2016/CR150039PR.pdf
