In trademark infringement cases, it is sometimes helpful to have someone testify about likelihood of confusion. Typically, courts allow a witness with personal knowledge to testify about what they saw or heard. However, some witnesses don’t have personal experience about the facts in a case but they may have specialized information which may be helpful for a jury to hear. These are typically referred to as expert witnesses. They are not fact witnesses.
There are standards that must be met for admissibility of expert testimony in trademark infringement litigation. Experts may have their methods challenged before they take the stand. Expert testimony may be excluded as speculative and unreliable if an expert’s methods are not based on sufficient facts or data, are not reliable, or are not applied reliably to the facts of the case.
The trial court judge acts as a “gatekeeper” to ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable. Every expert is subject to a reliability test. Courts analyze expert testimony using the following five, non-exclusive factors in order to determine whether an expert’s reasoning and methodology are reliable:
- Whether the theory or technique on which the expert relies has been tested;
- Whether the theory or technique has been subject to peer review and publication;
- The known or potential rate of error of the technique or theory when applied;
- The existence and maintenance of standards controlling the technique’s operation; and
- Whether the theory or method has been generally accepted by the expert community.
Appellate courts review how the trial court judge tests an expert’s reliability under the abuse of discretion standard, which is the same standard used to review the admission or exclusion of expert testimony. When seeking expert testimony, it is critical that the expert’s credentials and methodology be sufficient to withstand court scrutiny.