Police test drivers for THC with field sobriety tests

The ‘high’ price of driving under the influence

Girlfriend snaps phone image of suspect as he performs one leg stand sobriety test while eating Del Taco burrito. (Andrea Clemett/ Lariat)

Since the California state legalization of marijuana, police can test drivers for positive THC for DUI. Traces of THC can be difficult to detect according to authorities and lawmakers, as it is dissimilar to alcohol and other drugs which may be detected through blood and urinalysis within hours of usage. Police will conduct impairment of THC with a field sobriety test and from the results can determine if an arrest is necessary for those suspected of driving under the influence.

California law enforcement officials use a series of mental and physical activities to test sobriety as driving under the influence of marijuana may impair lane tracking, cognitive function as well as debilitate psychomotor skills according to the National Highway Traffic Safety Administration. The three regulated tests are known as the horizontal gaze nystagmus, the walk and turn and the one-leg stand test.

An officer performs the horizontal nystagmus test by using their finger or an object and moving it from side to side; within close proximity to a person’s face. Using this task to expose spontaneous twitching of the eyes correlates with the degree of intoxication.

Normally, a person’s eye will twitch after strained staring beyond 45 degrees but if it would be alarming the eye jerked at or below the 45 degree marker. If persons are diagnosed with a nystagmus, they are required to provide a doctor’s note stating their condition and at which the officer is allowed to perform a finger smell test for marijuana residue.

The suspected offender will walk in a straight line in the walk and turn test, at which point the officer will provide specific instructions drawing attention between mental and physical tasks. The officer will rule intoxication if the suspect forgets the number of steps, takes breaks in walking, stops to consume food or uses repeated language such as “dude,” “bro” or “chillax.”

The final test the police conducts is the leg stand, in which the officer will ask the suspect to look down, count, remain still and raise their foot. If any alarming behaviors occur like swaying, drowsiness, munchies, paranoia of the exam or forgeting the task itself, then the officer would make an arrest.

If the officer has reason to believe the suspect has been under the influence, they may follow with a drug swab test which takes eight minutes to develop if a person’s saliva carries THC. Although tests can reveal residual THC in saliva up to three days following consumption.

The NHTSA is currently working with law enforcement and scientists to advance the department’s understanding of drug-impaired driving. During the following year, the agency will produce new oral fluid screening devices that will account for drugs by the drivers in less time. It will also collect increased detailed data for the fatal crashes caused by drug-related occurrences in 2018.

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