Expert Testimony Needs Judges to Act as “Gatekeepers”: The Maryland Court of Appeals Teaches Why

The lawof evidence hasmany rules to help guide a jury or other trier of fact to reach a just result. Lay witnesses must confine their testimony to matters within their own personal knowledge. Hearsay, generally speaking, is not permitted. Evidence must be directly relevant to the issues before the court, and overly prejudicial evidence must be excluded. Judges who do their best handling the hundreds of evidentiary issues that may arise in a case can still make a mistake in the heat of trial. But errors in any of these areas are usually not fatal to the truth being determined by a jury. In one area, however, the failure to apply evidentiary rules faithfully can often prove outcome determinative: the admission of expert evidence. Allowing an expert to testify when that expert’s testimony is not firmly grounded in science or another technological field can mean the difference between an innocent person being found guilty of a crime or an individual or business being subject to civil liability for harm that the person or entity did not cause. There have been thousands of cases and scores of articles regarding the standards judges should apply in decidingwhether to admit expert evidence given these high stakes. The distinguished Federal Rules Standing Committee on Rules of Practice andProcedure is presently consideringwhether to amend Federal Rule of Evidence 702, which addresses the admissibility of expert evidence, to make clear that a proffered expert’s methodology, as well as the expert’s conclusions, must be reliable before that expert’s testimony can be presented to a jury. Despite regular discussion of the subject of expert testimony, it remains relatively rare to find a judicial opinion that thoroughly analyzes and sets forth clear guidelines for trial judges regarding the admissibility of expert evidence. In