Wisconsin’s New Roadside Drug Testing Law: What Drivers Need to Know

Wisconsin just changed how police investigate suspected drugged driving.

As of March 2026, law enforcement officers can now use roadside saliva tests during traffic stops to screen drivers for drugs. The technology was previously tested in a Dane County pilot program, where results aligned with later blood tests.

Here’s what that actually means and what it doesn’t mean.

What’s New?

Under the new law signed by Governor Tony Evers, police can now:

• Take a saliva sample (oral fluid test) at the roadside.
• Use it to screen for drugs like THC, opioids, and stimulants.
• Do this before an arrest to help determine next steps.

These tests are intended to function similarly to a preliminary breath test (PBT) for alcohol, which is a quick screening tool used during a stop.

What the Saliva Test Actually Does

The key thing to understand is that this is a screening tool, not a proof of guilt.

The test checks for the presence of drugs in your system. It does not actually measure impairment, and it also does not determine whether you’re legally guilty.

Law enforcement officials have been very clear on this point. The results are “strictly preliminary.” They are used to help establish probable cause for arrest or further testing, and to help officers decide whether to pursue confirmatory testing (usually a blood draw).

Can These Test Results Be Used in Court?

No, not to prove guilt. The roadside saliva test itself is not admissible to show you were impaired. It is only used to justify and arrest and/or a request for a chemical test (like blood testing)

This is similar to how roadside breath tests are used in Wisconsin. These tests are mainly used to support the officer’s decision-making, not to convict you.

When Can Police Use the Test?

Officers still need probable cause to believe you’re impaired before administering the test.

That means:

• They must observe signs of impairment (driving behavior, physical indicators, etc.).
• The test is not random or automatic.

What the Tests Detect

These saliva tests can identify the presence of substances such as THC (marijuana), opioids, and stimulants (like amphetamines). They do not measure how much of the drug is in your system or whether you are actually impaired.

Important: Presence ≠ Impairment

This is one of the most important legal nuances. The test only shows that a drug is detectable. It does not prove you were impaired while driving.

However, in Wisconsin, for certain controlled substances, any detectable amount can still create legal risk. This makes confirmatory testing (like blood tests) extremely important in a case.

What Happens After a Positive Test?

If the roadside test indicates drugs may be present:

1. The officer may establish probable cause.
2. You may be arrested.
3. You may be required to submit to a chemical test (typically blood).
4. That lab test — not the saliva test — becomes key evidence.

Charged With OWI in Wisconsin? Get in Touch Now.

Attorney Patrick J. Stangl has over 30 years of experience defending OWI cases across Wisconsin, including complex cases involving parked vehicles, actual physical control, and modern vehicle technology.

Attorney Patrick Stangl explains why you should never give up hope when fighting repeat DUI/OWI charges in Wisconsin:

Criminal Defense Lawyer Patrick J. Stangl has been aggressively fighting to protect the rights of drivers accused of OWI and other drunk driving charges for over 30 years. He remains committed to protecting the innocent against OWI charges across Wisconsin.

If you need help to fight drunk driving charges in Wisconsin, Attorney Pat Stangl is happy to offer you a FREE 10-minute consultation to discuss your case and explore options for your defense against OWI, DUI, DWI, PAC, BAC, or other criminal charges.

If you’re in need of a criminal defense attorney with years of experience with OWI-related cases in Wisconsin, contact Attorney Patrick Stangl today.