Field Sobriety Tests (FSTs) were originally designed to measure impairment from alcohol. They measure things that are correlated to driving impairment where tha

Field Sobriety Tests (FSTs) were originally designed to measure impairment from alcohol. They measure things that are correlated to driving impairment where that impairment is the result of alcohol use. The correlations would be different for a driver who is under the influence of marijuana.