With one in five Americans living in states with legal cannabis, it stands to reason that more drivers may be driving while under the influence. Research has shown a slight increase in marijuana DUI activity, but not enough to definitively regard it as an epidemic. But with traffic fatalities reaching its highest level in five decades, law enforcement is being pressured to crack down on impaired driving, whatever the influence may be.
Alcohol levels are easily determined using a breathalyzer, a device that’s been around for decades and has a proven track record in accuracy. Used in conjunction with a field sobriety test, police officers can determine within minutes whether a driver is truly impaired.
No such test for marijuana exists, although there are some potential methods currently being developed. Police must use the field sobriety tests, or more controversial methods that involve physiological observation and can prove to be inaccurate. Symptoms like tachycardia, hypertension and other physical symptoms are used to determine marijuana intoxication, in conjunction with a blood test.
Unfortunately, these methods are not reliable. Tachycardia and hypertension are symptoms that can be attributed to numerous conditions and therefore serve as supplementary evidence in court. Physical observations can also be subjective, especially to a police officer who is not a trained medical professional. Blood tests are accurate in determining if a person has used cannabis within the past month. By measuring the amount of unmetabolized THC in the blood, the test can prove how recently someone consumed cannabis.
In Washington State, five nanograms per milliliter is the legal limit for marijuana, but that number is not based on any valid science. “Everyone is looking for one number,” said Marilyn A. Huestis, a senior investigator at the National Institute on Drug Abuse. “And it’s almost impossible to come up with one number. Occasional users can be very impaired at one microgram per liter, and chronic, frequent smokers will be over one microgram per liter maybe for weeks.”
Huestis brings up the issue of tolerance, which is common among medical marijuana patients like Greg. He submitted to a blood test after a traffic stop and his THC levels were at 22-nanograms per milliliter, well over the legal limit. Because of his tolerance due to a daily dose of cannabis, Greg says that he is “completely functional” when using marijuana. But under Washington state law, Greg has been charged with a DUI.
In order to prove his innocence in court, Greg’s defense will have to use scientific evidence that proves the legal limit is inaccurate, which may inspire lawmakers reconsider legal limits for marijuana.