Legalization efforts spur many heated conversations, one of which is often focused on cannabis DUI detection. Law enforcement hasn’t standardized or widely accepted any method for detecting high drivers. Even a blood test wouldn’t show the time of inebriation.
It’s still hard to know whether someone had consumed 30 minutes or six hours before being pulled over. This nuance, combined with the piecemeal way marijuana is legal in the U.S., means that cannabis DUI detection and protocol varies between departments.
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Cannabis DUI tests across the U.S.
Orange County, Calif. Sheriff’s deputies detect stoned driving using the methods developed to identify drunk drivers on the road.
Sergeant Frank Gonzalez, a public information officer for the Orange County Sheriff’s Department, told GreenState, “The same cues for alcohol-impaired driving are used for cannabis-impaired driving: speeding, lane straddling, unsafe lane changes, vigilance issues, no headlights on during darkness, et cetera.”
Minneapolis, Minn. officers use in-field sobriety tests, according to media relations coordinator Aaron Rose.
“If someone is suspected of DWI for marijuana, and there is specific articulable evidence documented,” Rose explained, “any officer can do a standard DWI field test and submit a request for a blood warrant approved by a judge. The standard blood testing will take place in a hospital setting.”
Blood test versus saliva for cannabis detection
A blood test can accurately detect cannabis in the system but may not tell when it was consumed. That last bit is significant when being charged for driving on weed. Recently, a study confirmed this, showing that cannabis stays stored in a regular consumer’s fat cells. In the research, stoner participants tested positive for cannabis but weren’t legally impaired.
Many also argue that it is an invasion of privacy to draw blood, and it remains within someone’s rights to turn down a blood test.
Police in certain Minnesota jurisdictions spent the last year engaging in a pilot program for two roadside saliva intoxication tests that also detect opioids and methamphetamine. The devices could only be used with the consent of the detained, and results were not permissible in court. This program ended at the beginning of the year, and the state is now preparing the results into a report.
After officers suspect that someone is driving under the influence of cannabis. It’s time to prove their suspicions–this is when things get a bit arbitrary.
How officers detect marijuana DUIs
Back in Orange County, deputies are using alcohol DUI tests, like tracking eye gaze for abnormalities, balance tests like the one-leg stand, and the classic finger-to-nose. Whether someone needs the test depends on the deputy.
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“After a deputy completes their investigation and considers the totality of the circumstances, the deputy will form an opinion as to whether the driver is under the influence and can or cannot operate a vehicle safely,” said Sgt. Gonzalez. “This includes evidence gathered during the vehicle in motion, personal contact, and pre-arrest screening, which is the same for alcohol-impaired driving.”
Turns out, most officers are in a predicament when it comes to weed on the road. No method is widely accepted by law enforcement to detect driving while high. Additionally, there isn’t a set point of inebriation like 0.08 percent blood alcohol content with alcohol. 33 states have adopted a 5 nanogram limit of THC in blood to detect a DUI paired with “effects-based” evidence. Effects-based evidence is like what Gonzalez described, but 18 states make it far more complicated and to some, arbitrary.
What are “per se” cannabis DUI limits?
Many states have “per se” cannabis DUI laws that indicate a person is under the influence based solely on chemical test results. When it comes to weed, a blood test, or even a saliva test, can render positive results when a person is not impaired. That is the nature of how the body metabolizes the plant.
This poses issues for law enforcement seeking DUI detection methods. The National Highway Traffic Safety Administration deemed these limits “arbitrary and unsupported by science” in 2016. There are 18 states with per se marijuana DUI laws, where even if a person has shown no signs of impaired driving, a positive drug test could land them with charges.
States that have per se limits for THC:
- Colorado (5 μg/mL in blood)
- Illinois (5 μg/mL in blood, 10 μg/L in other bodily substances)
- Iowa (5 μg/mL)
- Montana (5 μg/mL in blood)
- Nevada (THC: 10 μg/mL, 2 μg/mL in urine / THC-COOH: 15 μg/mL in urine, 5 μg/mL in blood)
- Ohio (35 μg/mL in urine, 50 μg/mL in blood)
- Pennsylvania (5 μg/mL)
- Washington (5 μg/mL)
- West Virginia (3μg/mL in blood)
States with a zero tolerance per se limit for THC:
- Arizona
- Delaware
- Georgia
- Idaho
- Indiana
- Michigan
- Oklahoma
- Utah
- Rhode Island
- South Dakota
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In these states, having the allotted amount of THC in the system is grounds for a DUI, whether a person shows signs of impairment or not. Research indicates per se limits are “poor and inconsistent” when measuring the magnitude of impairment against THC concentrations in blood samples.
Cannabis stays in the blood far longer than it makes a person feel high. The same goes for urine concentrations. Saliva tests boast a more accurate timeline but pull false positives more frequently, which makes them less solid in court.
There is no guaranteed correct way to keep stoned drivers off of the road, but many believe that per se limits are among the less effective options. Observing erratic driving and looking for signs of inebriation may be necessary to ethically persecute high drivers. This would make “per se” laws out of the question.
No matter what the future of marijuana DUIs looks like, the best rule of thumb for weed and the road is to never drive high.
