The recreational use of marijuana remains illegal in New York, but police officers in the state still encounter drivers who appear to be under the influence of the drug on a regular basis, whether for allowed medical use or otherwise. There is currently no reliable way to determine whether or not a motorist is operating a vehicle while under the influence of marijuana, and this is a source of serious concern for law enforcement agencies across the country.
Breath, blood and field sobriety tests have been used for years to establish intoxication in drunk driving cases, but they are of little or no use to prosecutors when marijuana and not alcohol impairment is suspected. High levels of alcohol in the blood have been scientifically linked with diminished driving skills, but elevated THC levels mean very little. THC can linger in the system for weeks after marijuana has been smoked, and even significant quantities of the metabolite may not be enough to establish impairment beyond any reasonable doubt.
With chemical testing of little use in marijuana impairment cases, police departments have relied more heavily on field sobriety tests. These tests are very effective at revealing alcohol impairment, but those under the influence of marijuana may have little difficulty with them. This is because marijuana does not affect balance and coordination in the way that alcohol does, and these tests were not designed to pick up signs of marijuana impairment like slower reaction times and difficulty dealing with distractions.
Experienced criminal defense attorneys may urge prosecutors to drop impaired driving charges when they are not supported by credible and reliable scientific evidence. They could also be highly suspicious of any testing method used by police that has not been subjected to rigorous evaluation. Police sometimes go beyond the standardized field sobriety test by asking drivers to count or recite the alphabet backwards, and portable drug testing kits have been known to identify benign substances as illegal drugs.