What Happens at an OWI Traffic Stop in Michigan, Step by Step

A Michigan drunk-driving (OWI) investigation moves through a series of stages: the stop, the officer's observations and questions, field sobriety tests, a roadside preliminary breath test, an arrest, and then an evidential breath, blood or urine test. The stop, the PBT, the arrest and the evidential test each have their own legal standard.^{[2][11][7][12]} This page walks through the stages in order and links to the guides that cover each one in depth.

Stage	What the law requires
Pulling the car over	Reasonable, articulable suspicion of a violation of law.[2]
Keeping the driver at the roadside	The stop may not be prolonged beyond its purpose without new reasonable suspicion.[13]
Requiring a preliminary breath test	Reasonable cause to believe the person drove and that alcohol or a drug may have affected the ability to drive.[11]
Arrest	Probable cause: facts that would lead a prudent person to believe an offense was committed.[7]
Evidential chemical test	An arrest for a listed OWI-type crime, and a request by an officer with reasonable grounds.[8][12]

Step 1: The stop

When police stop a vehicle, the driver and passengers are "seized," so the stop must satisfy the Fourth Amendment.^[1] The standard is reasonable suspicion: the officer needs an articulable and reasonable suspicion that the vehicle or an occupant is violating the law, which is less than probable cause but more than a hunch.^[2] A stop supported by an observed violation is not invalid because the officer also had another reason in mind.^[14]

Michigan courts have held that a strong odor of intoxicants on a driver's breath can, standing alone, supply that suspicion.^[15] The U.S. Supreme Court has held that a reliable tip describing dangerous driving such as weaving or crossing the center line generally can too, though a bare claim of "drunk driving" is not enough.^[16] The Michigan Supreme Court has held that an officer's misreading of a clear statute cannot.^[17] The guide to when police may stop a car covers these rules and the cases behind them. Roadblock-style sobriety checkpoints are not allowed in Michigan.^[18]

A "stop" can also happen without a moving car. The Michigan Supreme Court has held that a parked driver may be seized when a patrol car blocks or partly blocks the way out, especially combined with spotlights and officers approaching from both sides.^[19][20]

Step 2: How long the stop can last

Police may not extend a traffic stop beyond the time needed to handle the violation that justified it unless the stop produces new reasonable suspicion.^[13] An odor of intoxicants noticed during the stop is one thing Michigan courts have said can support reasonable suspicion of drunk driving.^[15]

Step 3: Questions at the window

Under Berkemer v McCarty, roadside questioning of a motorist detained in a routine traffic stop is not "custodial interrogation," so Miranda warnings are not required at that point.^[3] Michigan's Court of Appeals says the same: a motorist detained for a routine traffic or investigative stop is ordinarily not in custody for Miranda purposes.^[4]

That changes if the driver is treated as being in custody for practical purposes; then the full Miranda protections apply.^[3] The way a person speaks is treated differently from what the person says: slurred speech is physical, not testimonial, evidence.^[21] See Miranda warnings and OWI stops.

Step 4: Field sobriety tests

The officer may ask the driver to step out and perform field sobriety tests. Michigan law defines a "standardized field sobriety test" as one of the tests validated by the National Highway Traffic Safety Administration (NHTSA), given in substantial compliance with NHTSA's standards.^[22] NHTSA's own manual tells officers the tests are a tool for seeing visible signs of impairment and "are not a pass/fail test."^[23]

A qualified witness may testify about these tests, including the horizontal gaze nystagmus (HGN) eye test, and nonstandardized tests may still be admitted if they meet the rules of evidence.^[24] The details are in the guides to field sobriety tests and the HGN test.

Step 5: The roadside preliminary breath test (PBT)

A PBT is an on-site breath test to detect alcohol or drugs in the body.^[25] Under MCL 257.625a(2), an officer may require one if the officer has reasonable cause to believe the person was operating a vehicle in a public or generally accessible place and that alcohol, a controlled substance or another intoxicating substance may have affected the person's ability to drive.^[11] The trigger is lower for drivers under 21 (any bodily alcohol content) and for commercial vehicles (any measurable amount).^[11]

• Under the current State Police rule, a PBT may be given only by a certified operator, after the operator determines the person has not smoked, regurgitated or put anything in the mouth for at least 15 minutes.^[26]
• Refusing a lawfully requested PBT is a civil infraction for most drivers.^[5]
• A commercial-vehicle driver who refuses commits a 93-day misdemeanor and is ordered out of service for 24 hours.^[6]
• An officer may arrest based in whole or in part on the PBT result.^[27]
• In an OWI prosecution or license hearing, the result is admissible only for limited purposes, such as deciding a challenge to the validity of the arrest.^[28]

More detail is in the preliminary breath test guide.

Step 6: The arrest

An arrest requires probable cause, judged on the totality of the circumstances known to the officer at the moment of arrest.^[7] Michigan statutes give police specific warrantless-arrest powers in OWI cases: after a crash, the officer may arrest a driver the officer has reasonable cause to believe was operating in violation of the OWI statute, even without seeing the driving.^[29] An officer may also arrest a person found in the driver's seat of a parked or stopped car that intrudes into the roadway.^[30] The State Police say a driver can be arrested at any alcohol level if the officer believes the driver is impaired.^[31] See probable cause for an OWI arrest.

Step 7: The evidential test after arrest

Once a person is arrested for an OWI-type offense, Michigan's implied consent law treats the driver as having consented to chemical tests of blood, breath or urine.^[8] The officer must give five advisements, including that the person may have an independent test, that results are admissible, and that refusing will result in a license suspension and 6 points.^[9] If the person refuses, no test may be given without a court order, but the officer may seek one.^[10]

After a refusal, or a test showing an unlawful alcohol level or a drug, the officer takes the plastic license on the Secretary of State's behalf and, if the driver is otherwise eligible, issues a paper temporary permit.^[32] A driver who refused has 14 days from the date of the officer's written notice to request a hearing.^[33] The next stages are covered in Michigan's implied consent law, refusing a breath or blood test and what happens after an OWI arrest.

What people commonly get wrong

• "No Miranda warning means the case is thrown out." Miranda governs custodial interrogation; ordinary roadside questions at a routine stop are not covered.^[3][4]
• "Taking the roadside test means I don't have to take the one at the station." Submitting to a PBT does not excuse the later evidential test.^[34]
• "Refusing everything means there is no evidence." Police may seek a court order for a test after a refusal, and other evidence of impairment is still allowed.^[10][35]

Practical point: after a stop, it helps to write down, as soon as they can, the time, place, what was said and which tests were requested. Keep any paperwork the officer handed over, including a temporary permit or refusal notice.