Expert opinion testimony

Using opinions of an expert witness (expert opinion testimony) calls for a threefold approach:

Two primary tests (or some variant of them) govern the admission of the opinions of experts. One is the Frye test; the other is the Daubert test.
 * Identify the issues that will require an expert opinion
 * Identify a qualified expert
 * Ensure that the qualified expert will use an admissible method.

Daubert governs in federal court
Daubert has replaced the Frye test, both in federal court and in many state courts, with a test where the trial judge determines the admissibility of expert opinion testimo­ny based on its relevance and the reliability of the underlying scientific techniques. The U.S. Supreme Court suggested that whether scientific expert opinion evidence will be helpful to the trier of fact may turn on whether: (1) the scientific technique can be— and has been—tested; (2) the technique has been subjected to peer review and publica­tion; (3) there is a known or potential rate of error; and (4) the technique has been generally accepted by the relevant scientific community.

The Court made clear in Daubert and subsequent cases that this list is neither a rigid nor an exhaustive set of requirements.Daubert is generally seen as the U.S. Supreme Court’s suggestion that trial courts act as “gatekeepers” to limit the admissibility of “junk science” and encourage the development of reliable scientific and technological forensic techniques. Recent changes to article seven of the Fed.R.Evid., which governs the admissibility of expert opinion testimony, are based on Daubert and its progeny. Kumho Tire Co., Ltd. v. Carmichael extended Daubert to technical areas other than those considered strictly scientific.

Technical expert opinion testimony is admissible under Fed.R.Evid. 702 (as amended in 2000) if “(1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness had applied the princi­ples and methods reliably to the case.”

2. Many States still use a version of the Frye test
Frye allowed scientific techniques to be admitted in court if they are generally accept­ed within the relevant scientific community. As the Court of Appeals for the District of Columbia Circuit stated in Frye, “courts will go a long way in admitting expert testimo­ny deduced from a well-recognized scientific principle or discovery, [but] the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.”

As examiners employ new software and updated versions of older software in their examination of digital media, they may face Frye or Daubert challenges to that soft­ware. As examination techniques develop and as expert witnesses deduce opinions about facts and evidence, “the thing from which the deduction is made must be sufficiently established” so as to be relevant and reliable in court.