Commonwealth v. Gerhardt

In this case we are asked to consider the admissibility of field sobriety tests (FSTs) where a police officer suspects that a driver has been operating while under the influence of marijuana. Police typically administer three FSTs — the “horizontal gaze nystagmus test,” the “walk and turn test,” and the “one leg stand test” — during a motor vehicle stop in order to assess motorists suspected of operating while under the influence of alcohol or other drugs. These tests were developed specifically to measure alcohol consumption, and there is widespread scientific agreement on the existence of a…