Imagine if you had to tell a family that their child was never coming home again...because a driver had a few too many drinks and they were too lazy to get a taxi? How would you feel if it was your child? Your brother, your parent, your best friend? Now imagine that you're the one who had a few drinks and thought...Home isn't too far. I'll make it without getting busted. While on the back streets worrying if the booze bus will catch you, you hit someone. How do you live with that for the rest of your life?Oral-fluid tests and training are helping officers track down potential impairment
Identifying when a driver is impaired by marijuana has long been difficult, partly because there isn’t a reliable drug test for impairment like there is with alcohol. Urine tests are useless because they can be positive for several days. Blood tests take time and relay levels of THC, the psychoactive compound that makes people high, that aren’t correlated with impairment. Field sobriety tests rely on the judgment of police officers, the vast majority of whom aren’t trained to look for cannabis impairment.
Newer methods, such as roadside monitors that test a person’s saliva for marijuana are providing officers with some help. But they can only detect recent use, not the level of impairment, unlike tests for alcohol where levels in the blood, saliva, or urine are more closely related to impairment, say toxicologists.
Alcohol is water soluble and establishes a uniform concentration across tissues and organs, making it a reliable gauge of impairment. But THC is fat soluble and sequestered from the blood by the brain and other fatty tissues.
The concentration of THC in your blood falls by about 50% every 17 minutes even as impairment increases, said Barry Logan, president of the Centre for Forensic Science Research and Education. By the time someone is pulled over, arrested and taken to a hospital for a blood sample, hours have often passed.
More drivers in fatal accidents are testing positive for marijuana in states that consistently test.
Roadside oral-fluid tests give a yes or no answer, much like a home pregnancy test. Officers ask a driver to move a stick or swab around in their mouth. Testing kits vary but mostly involve officers using a swab or sponge on a driver’s cheeks and under their tongue. They then stick the device in a test tube or read them directly on a built-in indicator, which alerts law enforcement if there is at least a certain amount of THC in the driver’s system. The results typically come within about 10 minutes.
Alabama was among the first states to start using the tests in 2018. They have since gone into widespread use in other states including Michigan and Indiana. In New York, lawmakers are considering a bill requiring the tests if law enforcement requests them after a crash.
In a 2023 review of roadside monitors used in Alabama by officers over five years, THC was detected in 90% of oral fluid versus 75% of blood samples from the same individuals.
When traces of cannabis are found, it still requires an officer’s judgment on whether the person is impaired. That means more training could help officers make better calls, law-enforcement officials say.
“It’s basically like a big puzzle that we are starting to piece together,” said Ryan Hutton, a state law-enforcement officer and founder of Extract-ED, which runs a program to teach police officers around the country how to identify whether a driver is impaired from cannabis.
Officers at the training watch as volunteers smoke cannabis and shortly after are put through roadside tests that drivers would experience if they were pulled over. If volunteers consume edibles, officers wait 60 to 90 minutes before testing. They check for the smell of marijuana, bloodshot eyes, lethargic movements and difficulty dividing their attention. When asked to provide a license and registration, the training showed that people who are high often only produce one or the other.
Cannabis can also scramble a person’s internal clock, he said. When officers tell a person to put their head back, close their eyes and say when 30 seconds have passed, people who are high might stop after 10 seconds or wait more than a minute.
The concentration of THC in your blood falls by about 50% every 17 minutes even as impairment increases. “When you’re driving, you’re always judging time and distance. You need to know where to stop, accelerate, pass, press the brake,” Hutton said.
Outside Charlottesville, Va., in 2018 a dump-truck driver drove around a barrier and onto railroad tracks as an Amtrak train sped toward him, horn blowing. The crash derailed the train, killed a passenger in the truck and injured nearly a dozen people. Witnesses said that the truck had plenty of time to cross but that the driver paused, unable to quickly determine how to get around the second barrier.
The driver had used marijuana, likely impairing his reaction time, investigators said. They said that the driver’s blood showed he had used marijuana, but that they couldn’t determine whether he was high.
