Decision Commonwealth v. Gerhardt

Date: 09/19/2017
Organization: Massachusetts Supreme Judicial Court

Table of Contents

Commonwealth v. Gerhardt

Commonwealth v. Gerhardt
Supreme Judicial Court, September 19, 2017
(Evidentiary Issues/Marijuana Impairment)

The fact that marijuana can cause impairment of an individual’s driving skills is within the common experience and knowledge of jurors, therefore, a police officer may testify as a lay witness to a defendant’s performance on field sobriety tests to the extent they are relevant to skills required to operate a motor vehicle safely. However, in order for a police officer to testify to the correlation between marijuana impairment and a defendant’s performance of field sobriety testing, that officer must be qualified as an expert witness.


The term ‘roadside assessments’ should be used in lieu of ‘field sobriety testing’ in a marijuana impairment case. “[A]n 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.”