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What to do if you’re pulled over after using cannabis

Despite legalization efforts in the area, motorists can still be convicted of driving under the influence of cannabis.

Customers waited in long lines to buy marijuana at Cannabist in Deptford, N.J. on April 21, the first day recreational sales became legal. But lawyers warn against driving after using the drug.
Customers waited in long lines to buy marijuana at Cannabist in Deptford, N.J. on April 21, the first day recreational sales became legal. But lawyers warn against driving after using the drug.Read moreELIZABETH ROBERTSON / Staff Photographer

Pennsylvania’s medical marijuana program went into effect in 2018, while New Jersey began allowing recreational sales of cannabis in April 2022.

But beware: Despite these legalization efforts and those in other states, motorists can still be convicted of driving under the influence of cannabis.

In Pennsylvania, DUI is defined as driving with “any amount” of a controlled substance or its metabolites in the blood. With cannabis, the chemicals in question can be detected in the blood for days after use — long after any “high” or impairment has worn off.

In New Jersey, a DUI conviction requires evidence of actual impairment. That includes the officer’s opinion that the person was driving unsafely, coupled with other findings such as drugs in the car. In addition, prosecutors typically enlist the input of a second police officer with specialized training, called a drug recognition expert. But the state Supreme Court is in the midst of reviewing whether such findings should be admissible as expert testimony.

Here’s how to stay safe and reduce the risk of legal trouble:

Can I drive after using cannabis?

It may seem obvious, but the safest route is to avoid driving after using cannabis.

If you must drive, research suggests that impairment has mostly worn off by five hours after inhalation, said Tory Spindle, a psychologist at the Johns Hopkins University School of Medicine.

For edibles, a person should probably wait at least six hours, as the active components of the drug generally take longer to dissipate than when it is smoked, Spindle said. But for both types of use, the drug’s effects and the duration of those effects vary from person to person.

In a July 2021 analysis in the journal of Neuroscience & Biobehavioral Reviews, Australian researchers found that most driving-related skills are predicted to recover within five hours of inhaling the drug, and “almost all” should recover within seven hours.

» READ MORE: He was arrested for DUI nearly a week after using cannabis, long after the 'high' wore off

How can I tell if I’m impaired?

If there is any doubt, wait.

Cannabis users can usually tell when they’re high, but they may be unable to detect subtle impairment that lingers after the initial effects have subsided, said Robert Pandina, a neuropsychologist and professor emeritus at Rutgers University.

Technology may help determine if you’re impaired.

One option is a smartphone app called Druid, developed by Michael Milburn, a psychology professor at the University of Massachusetts Boston. The app enables users to measure their reaction time, hand-eye coordination, balance, decision-making accuracy, and the ability to estimate the passage of time.

It is designed for individual use, not for law enforcement, as there is no specific outcome that signifies impairment. Instead, the app indicates whether the individual’s performance is significantly worse than their baseline measurements, which must be taken on a previous occasion when that person has not been using drugs.

Is there a ‘Breathalyzer’ for pot?

Cannabis is not like alcohol, for which the “Breathalyzer” and similar devices provide a reliable estimate of blood alcohol content, which in turn is correlated with ability to drive.

In New Jersey and many other states, motorists should be wary — the determination of impairment is partly up to the officer’s discretion, said William J. McNichol Jr., an adjunct professor at Rutgers Law School in Camden.

That advice may be particularly important for Black people, who have been arrested in disproportionate numbers for cannabis-related offenses, he said.

When human judgment is involved — even from the trained, drug recognition experts (DRE) whose protocol is now under review by the New Jersey Supreme Court — the risk of improper arrest is higher, McNichol said.

“The DRE is really ripe for either explicit, mean-spirited bias or implicit unknown bias,” he said.

Law enforcement officials counter that the DRE program is grounded in years of research and that in the absence of a reliable chemical test for impairment, the protocol is essential in keeping roadways safe.

Should cannabis users drive extra carefully?

Yes, says State Rep. Chris Rabb (D., Philadelphia), a medical marijuana patient who drives 100-plus miles to Harrisburg for work.

Rabb said he takes a tincture of cannabis several nights a week to combat sleeplessness, a side effect of post-traumatic stress.

That means his blood likely always contains at least trace amounts of THC — the main active substance in cannabis — or its metabolites. In Pennsylvania, that means he can be arrested for DUI, even though he never drives until the morning after using the drug, when any effects have worn off, the lawmaker said.

“I drive very carefully,” he said, “but I drive with fear.”

Rabb has introduced legislation that would exempt medical marijuana patients from this “zero-tolerance” law, provided they are driving safely.

Quari Williams, 23, a Bensalem resident and medical marijuana patient, said he was arrested on DUI charges six years ago despite not being impaired. Since then, in addition to driving carefully, he takes pains to keep his car in good shape. He also refrains from driving after smoking cannabis.

“Be smart about it,” he said. “Make sure that everything in your car is fine. Your inspection and registration and things like that, things that can get you pulled over.”

Should I show my medical marijuana card?

In Pennsylvania, absolutely not.

That’s the advice from defense attorneys Patrick Nightingale, who practices in Pittsburgh, and Ken Chotiner, who is based in Philadelphia.

“I have had a number of clients about to be let go from a traffic stop until it came to light they were a medical cannabis patient,” Nightingale said.

That admission gives police reason to suspect that the motorist’s blood contains at least trace amounts of cannabinoid chemicals. They can then ask the driver to submit to a blood test. And if the motorist refuses, that means an automatic loss of your driver’s license for a year. If police convince a judge there is probable cause to believe the person has been using cannabis, they can get a warrant to compel a blood draw.

In New Jersey, where a blood or urine test is not enough for a conviction, there is less risk in disclosing medical marijuana status, said Michael A. Hoffman, a defense attorney based in Vineland. But there’s no particular reason to volunteer it, either.

What information should I volunteer?

As little as possible, Chotiner said. But never lie.

“Be very polite,” he said. “But you’re not under any obligation to answer questions or provide information, other than your name and your driver’s license,” along with proof of insurance and registration. Even if the officer acts suspicious, resist the urge to be helpful, Chotiner said.

“I’d much rather the officer testify, ‘He wasn’t answering my questions, so I arrested him,’ rather than ‘I asked him, and he volunteered.’”

Should I agree to a blood or urine test?

It might make sense for a motorist to agree to a blood test if it’s a first DUI offense, said Brad Shuttleworth, a defense attorney in Philadelphia. First-time offenders are eligible for a “rehabilitative” program that would lead to a year’s probation but a loss of license for just 60 days. After that, they can have their record expunged.

In New Jersey, on the other hand, motorists can decline to provide a blood or urine specimen “with no legal repercussions,” according to a brief filed in the Supreme Court case by the state’s association of county prosecutors. (Though if officers have probable cause to suspect drug impairment, they can obtain a warrant to get a sample.)

Can I fight a DUI in court?

A lawyer can try to challenge the evidence in a DUI arrest.

One option is filing a motion to suppress the results of a blood test, arguing that police didn’t have probable cause to take you into custody and obtain a blood sample, Shuttleworth said.

Another option is questioning the toxicologist about whether the testing device was properly calibrated, Chotiner said.

“With a DUI defense, I am dotting the i’s and crossing the t’s to make sure the government did everything the right way,” he said.