Archives – June, 2016


by: Dennis J. Ryan, an ALM Listing Expert

Recently, the National Commission on Forensic Science published a Views Document by the Subcommittee on Reporting and Testimony dealing with the terminology “Reasonable Degree of Scientific Certainty” or any variation of the term which may be discipline-specific.  The Commission was highly critical of using the term in testimony by forensic experts, and suggested that the scientific community should not encourage the use of this terminology. The Commission recommends abandoning this phrase, which has been used for many years in courts across the United States.  The Commission admits that there is no clear alternative to the term “reasonable degree of scientific certainty,” and they admit that work is needed in this area to strengthen terminology for expressing an expert’s opinion.

The term “reasonable degree of scientific certainty” is not defined in any standard medical or scientific journals; rather, it is a legal term that was first linked to opinion testimony in a 1969 case (Twin City Plaza Inc. v. Central Surety & Ins. Corp 409 F.2d 1195, 1203 (8th Cir. 1969). The Daubert-related cases, Daubert, Joyner and Kumho, and the Federal Rules of Evidence 702-705 do not require any similar language.  The Daubert and Frye tests serve to exclude any speculative testimony and preclude the need for any such language relating to scientific certainty.

The Commission recommended that courts discontinue using the term “reasonable degree of scientific certainty” because it could result in confusion for those involved in court cases.  The commission states: “In the courtroom setting, the phrase risks misleading or confusing the factfinder” and “has no scientific meaning and may mislead jurors or judges when deciding whether guilt has been proved beyond a reasonable doubt.” In a 2014 case in Hawaii (State v. DeLeon, 319P.3d 382, 403 (Haw.2014) the court said “trial courts should not require a ‘reasonable degree of scientific certainty’ before admitting expert opinions.”

The lack of a common definition of this word across the sciences, or even within a discipline of science, is confusing and frustrating.  If one was to assemble a room of legal professionals, there would be a host of different definitions for the term, and no common definition would result.  The same would hold true for a room of scientific scholars. A juror may, on the other hand, have a totally different understanding of the term and may equate it to finding of proof beyond a reasonable doubt.

Much work is needed to strengthen the terminology a forensic expert uses to expresses their opinions. The goal is to minimize any misleading or confusing terminology.

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