Justices determined that there is a lack of scientific consensus as to the validity of FSTs for determining whether a subject is under the influence of cannabis. They opined: “There is ongoing disagreement among scientists, however, as to whether the FSTs are indicative of marijuana impairment. In recent years, numerous studies have been conducted in an effort to determine whether a person’s performance on the FST is a reliable indicator of impairment by marijuana. These studies have produced mixed results. … We are not persuaded … that the FSTs can be treated as scientific tests establishing impairment as a result of marijuana consumption.”
As a result, justices ruled that police may only provide limited testimony with regard to a defendant’s FST performance. An officer “may not suggest … on direct examination that an individual’s performance on an FST established that the individual was under the influence of marijuana,” the court determined. “Likewise, an officer may not testify that a defendant ‘passed’ or ‘failed’ any FST, as this language improperly implies that the FST is a definitive test of marijuana use or impairment.”
The court further ruled that a police officer may not testify “without being qualified as an expert [as] to the effects of marijuana consumption [or] offer an opinion that a defendant was intoxicated by marijuana [because] no such general knowledge exists as to the physical or mental effects of marijuana consumption, which vary greatly amongst individuals.”
Attorneys Steven Epstein and Marvin Cable filed an amicus curiae brief in the case on behalf of national NORML.
The case is Commonwealth v. Gerhardt.