You roll your window down. The officer leans in. “Have you had anything to drink tonight?” Before you can answer, they’re unholstering a breathalyzer. But here’s what they’re not telling you: in most states, you don’t have to take that test—and saying no might actually help your case.

Roadside breathalyzer tests aren’t even admissible in court

The roadside breathalyzer isn’t a real courtroom tool. It’s mostly just leverage. According to LawInfo, “Preliminary breath test (PBT) devices are not as accurate, and the prosecutor cannot use them to prove impairment.”

But PBT results can be an excuse to arrest you. LawInfo says the test “can give police officers probable cause to make an arrest.” That’s the real point of the roadside breathalyzer. It’s not about justice. It’s about justification. And here’s the kicker, in 46 states it’s completely voluntary.

Michigan is one state where you “must” take a roadside breathalyzer test. But one Michigan defense firm breaks it down even further: “If you refuse to take an on-the-spot breathalyzer you can be fined up to $150 plus court costs.” That’s it. In Michigan, refusal is a civil infraction—not even a misdemeanor.

Why some drivers should just say no

The roadside breathalyzer test isn’t just sketchy—it’s prone to false positives. One Redditor warns, “Breathalyzers are notoriously inaccurate that’s why you never blow if you are sober.” Another adds, “You should refuse the physical field sobriety tests because that is extra evidence that it’s better the police don’t have.”

And if you’re doing keto or fasting? You could blow dirty while stone-cold sober. According to a study in the Journal of Analytical Toxicology, “Acetone may be found in human breath and may give a false positive result.”

Still not convinced? In Colorado, a man “blew twice at 0.00 and had a negative blood test and was still charged.” A Reddit commenter claimed, “The department paid a massive settlement to the citizen accused.”

Refusing a roadside breathalyzer won’t stop the arrest

Let’s get real. Refusing the roadside breathalyzer test might not stop the cuffs. But it can help in court. LawInfo notes, “Even if you do refuse, you can still face prosecution in a DUI case.” But with no BAC reading, the prosecution’s job gets harder. The roadside breath test might look official, but it’s more bluff than bite. If you know your rights, you don’t have to play along. Just remember—saying “no” politely could be your best defense.