Swab and Order: New bills would let Michigan cops test your spit for weed

Lawmakers want cops to roll out roadside saliva tests to catch stoned drivers. But experts say the technology is unreliable and doesn’t actually measure impairment.

MICHIGAN—You could be sober. You could be legal. You could be driving just fine.

But if a new plan in Lansing becomes law, none of that may matter—because Michigan cops could still swab your mouth, test your spit for THC, and use the results to arrest you.

That’s the premise behind a pair of newly introduced House bills that would allow police officers across the state to use roadside saliva tests to screen drivers for THC and other drugs.

The bills were introduced in late April by state Reps. Brian BeGole (R-Antrim Township) and Julie Rogers (D-Kalamazoo) and have since cleared a committee with bipartisan support. 

Lawmakers say the proposal is about saving lives and giving officers better tools to keep impaired drivers off the road. But legal experts, defense attorneys, and civil rights groups argue the technology is flawed, the science doesn’t hold up, and the consequences could be serious.

What’s the Plan?

House Bills 4390 and 4391 would amend Michigan’s traffic laws to let all police departments begin using roadside saliva tests—also called “oral fluid analyses”—to screen drivers for drugs. Think of it like a weed version of a breathalyzer, but for spit instead of breath. 

Under current law, only specially trained Drug Recognition Experts (DREs) have been allowed to use this technology during limited state pilot programs. But under the new bills, any officer could now administer the test, and the results could be used to justify an arrest on the spot.

In short: If this legislation becomes law, Michigan cops would have a brand-new tool to test for drugs on the roadside—and cannabis users might be the first ones caught in the crosshairs.

Spit Test Déjà Vu

If this all sounds familiar, that’s because it is. Between 2018 and 2020, Michigan State Police ran two pilot programs using handheld saliva analyzers to detect drug use during traffic stops.

The results didn’t exactly inspire confidence: Those tests produced false positives or false negatives in nearly one in four cases, often flagging sober drivers or missing actual impairment.

Despite that shaky track record—and the state’s own report concluding there’s no reliable link between THC levels and actual impairment—lawmakers are now pushing to make the testing program permanent and give police across Michigan even broader authority to use it.

In a press release, BeGole insisted those state test programs were a “success.”

“Officers who are protecting the public and keeping our roads safe need to be able to determine if someone is operating a vehicle while under the influence of drugs,” BeGole added. “By embracing this technology, our state can save lives and be a leader in public safety.”

Rogers has defended the tests as a “complementary tool” meant to help officers build probable cause during traffic stops. But the fine print tells a different story.

According to a legislative summary, the new laws would allow cops to make arrests based solely on roadside spit tests—regardless of any other impairment tests or growing evidence that the presence of THC in saliva doesn’t reliably indicate whether someone is actually impaired. 

Questionable Testing

Here’s the biggest issue: These tests don’t measure whether someone is too high to drive. 

Science shows that THC, the active ingredient in cannabis, can stick around in your system for hours—or even days—after you’ve used it. And the roadside saliva tests being proposed in Michigan don’t gauge impairment. They simply detect whether THC is present in your spit.

That means drivers could be flagged—and arrested—for having used cannabis earlier in the day, the night before, or even the weekend prior. And that’s not just a hypothetical concern.

The state convened a commission to study this exact issue in 2019—concluding that there’s “no scientifically supported threshold of THC bodily content that would be indicative of impaired driving,” and finding a “poor correlation” between THC levels and actual impairment. 

In plain terms: Just because THC shows up in a test doesn’t mean you’re too high to drive.

None of this evidence has stopped state lawmakers from pushing forward. But it has put them at odds with leading cannabis researchers, defense attorneys, and public health experts who argue the technology that would be used to enforce these proposed laws is still unreliable and could lead to unjust arrests and court battles for stoners who didn’t do anything wrong.

“Improving road safety is an important goal, but these warrantless tests do nothing to advance that goal while creating multiple civil liberties concerns,” the ACLU said in a statement on the issue. “Drivers should not have to sacrifice their constitutional and civil rights for a roadside saliva test that is invasive, ineffective, and unreliable. And let’s face it, it’s also pretty gross.”

What Happens If You Say No?

The legislation also proposes penalties for anyone who refuses to comply with the test, regardless of whether you’re completely sober and ultimately cleared of any wrongdoing.

Just like a roadside breathalyzer, refusing to open your mouth for a police officer would result in a civil infraction—though some critics argue that might be the safest option on the table.

“Don’t spit,” attorney Michael Komorn told MLive. “Because the spit tests are junk science.”

The Bottom Line

Driving high is still illegal in Michigan. That hasn’t changed.

But these new bills could ultimately give police more power to arrest drivers for the presence of weed in their system—even if they’re not actually impaired. That has civil liberties groups, defense attorneys, and everyday stoners concerned about what might be coming next. 

The science isn’t settled. These tests aren’t reliable. But the push to change state law is still gaining new momentum—and that means your spit could be all it takes to land you in cuffs.

READ MORE: 6 quick hits of cannabis news from across Michigan

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