There is no question that some courts around the country require some type of certainty in the opinion being given by the expert. If the expert is to testify the expert must comply with the wishes of the court. There appears to some within the court system that are starting to disagree with the requirement. Remember it is from the decisions made by the court of appeals are where the interpretation of the law is made and directions are given as to what will be required. As more decisions by the court of appeals in different jurisdictions saying certainty is not an issue there will be less pressure to use these types of phrases. As an example, are the following cases.

In U.S. v. Mornan, Jackson, a forensic document examiner, explained her qualifications, her methodology, the bases for her conclusions, and the degrees of certainty with which she was able to reach her conclusions. Mornan nevertheless challenges the admissibility of her testimony based on the answer to one question on cross-examination. When the defense attorney asked Jackson whether her opinions were rendered to a "reasonable degree of scientific certainty," she replied, "I think they are." (App. at 455.) As the Government has pointed out, however, "there is nothing magical about the phrase, `to a reasonable degree of scientific certainty.'" (Brief for Appellee at 52.) It is not derived from the language of Rule 702 itself, and this Court has been unable to find any authority to support the position that questions regarding the expert's "degree of scientific certainty" categorically renders expert testimony inadmissible.

In the State of Ohio vs. Jazmine Westley, the Court of Appeals of Ohio Eight Appellate District stated that in State v. Thompson, 141 Ohio St.3rd 254, 2014, that court said, “expert witnesses in criminal cases can testify in terms of possibility rather than in terms of a reasonable scientific certainty or probability”.

Jim Mazerat
Forensic Investigations Group