The roadside preliminary breath test (PBT) in Michigan

The preliminary breath test, or PBT, is the handheld test an officer may require at the roadside before deciding whether to arrest.^[9][1] For most drivers, refusing it is a civil infraction rather than a crime, and its result has only limited uses in court.^[2][6] It is a different test, with different rules, from the evidential breath, blood or urine test requested after an arrest.^[8]

What the PBT is

Michigan law defines a "preliminary chemical breath analysis" as the on-site taking of a preliminary breath test to detect alcohol, a controlled substance, another intoxicating substance, or a combination in the person's body.^[9] The State Police make the rules for breath testing, and an instrument used for PBTs may also be used for evidential tests only if approved under those rules.^[10] Under the current rules, a Class I operator is certified to run a PBT and a Class II operator to calibrate PBT instruments.^[11]

When an officer may require a PBT

The trigger depends on the driver:

Driver	What the officer must have reasonable cause to believe
Any driver	The person was operating on a highway or other place open to the public or generally accessible to vehicles, including parking areas, and alcohol, a controlled substance or another intoxicating substance may have affected the person's ability to operate.[1]
Commercial motor vehicle driver	The person's blood, breath or urine contained any measurable amount of alcohol or any detectable presence of an intoxicant.[1]
Driver under 21	The person was operating with any bodily alcohol content as defined in MCL 257.625(6).[1]

What happens at the stop before the PBT, including field sobriety tests, is covered in what happens at an OWI traffic stop.

What refusing a PBT costs

Driver	Consequence of refusing a lawful request
Noncommercial driver 21 or older	Civil infraction.[2]
Driver under 21	Civil infraction and 2 points on the driving record.[3]
Commercial motor vehicle driver	Misdemeanor punishable by up to 93 days and/or a fine of up to $100, plus a 24-hour out-of-service order; the driver must be warned of this.[4]

Section 625a does not itself state the amount of the civil fine for a PBT refusal.^[2] A common misstatement is that an under-21 PBT refusal is a misdemeanor; under 625a(2)(d) it is a civil infraction, and only commercial-vehicle drivers commit a misdemeanor by refusing.^[2][12]

A different rule applies to minors outside the driving context. Under the minor-in-possession statute, if a minor does not consent to a PBT it may not be given without a court order, though police may seek one.^[13] The Court of Appeals struck down a local ordinance that allowed warrantless PBTs of minors in People v Chowdhury (2009); that case concerned a minor-in-possession ordinance, not the driving PBT.^[14] See minor in possession of alcohol.

How a PBT result is used

An officer may arrest a person based in whole or in part on a PBT result.^[5] In court, the uses are limited. Under MCL 257.625a(2)(b), a PBT result is admissible in an OWI-type prosecution or an administrative hearing only:

1. to help the court or hearing officer decide a challenge to the validity of an arrest;^[6]
2. if offered by the defendant, to rebut cross-examination testimony that the defendant's breath alcohol was higher at the time of the offense than at the evidential test; or^[7]
3. if offered by the prosecution, to rebut cross-examination testimony that it was lower at the time of the offense than at the evidential test.^[7]

In People v Parrott (2021) the Court of Appeals held this limit constitutional, noting that it treats defendants and prosecutors the same; a defendant may still offer expert testimony that alcohol levels were rising, but not through the PBT result.^[15] The rising-alcohol question is covered in rising BAC and the time-of-driving question.

The 15-minute rule for PBTs

The State Police rule now numbered R 325.2657a allows a PBT only by a certified operator, and only after the operator determines that the person has not smoked, regurgitated or put anything in his or her mouth for at least 15 minutes.^[16] The Traffic Benchbook still cites the older rule number, R 325.2655(2), and refers to approval by a different agency; since the 2023 rewrite, "department" in these rules means the Department of State Police.^[17][18]

In People v Robe (2021), an officer observed the driver for about three minutes before the PBT, with no evidence anyone else watched for the rest of the 15 minutes; the Court of Appeals held the result had to be excluded from the probable-cause analysis because the violation was significant and called its accuracy into question.^[19] On a second appeal in 2022, in an unpublished opinion, the court held the blood-draw warrant was not supported by probable cause without the PBT and sent the case back to decide whether the good-faith exception applied.^[20]

Not every flaw ends the analysis. In People v Mullen, an officer's warrant affidavit left out that the driver had a piece of paper in his mouth a few minutes before the PBT; the Court of Appeals still held a reasonable magistrate could have found probable cause, given nothing that significantly undercut the 0.15 result and other evidence of intoxication.^[21] The evidential-test version of the rule is on the 15-minute observation rule.

Very high readings

If a preliminary or evidential breath result is 0.35 or more, the operator must request medical assistance; failing to do so does not affect the result's validity.^[22]

The PBT does not replace the evidential test

A person who takes the PBT remains subject to sections 625c to 625f, the implied consent and refusal rules for the evidential chemical test.^[8] Refusing that later test has different, more serious license consequences than refusing the PBT.^[23] See Michigan's implied consent law and refusing a breath or blood test after arrest.

Common misunderstandings

• "The PBT number is what convicts you." The statute limits PBT results to arrest-validity challenges and narrow rebuttal.^[6]
• "Refusing the PBT means you cannot be arrested." The PBT is one possible basis for an arrest, "in whole or in part," and the general warrantless-arrest rules still apply.^[5][24]
• "Passing the PBT ends the stop." The officer may still request evidential testing after an arrest, and other admissible evidence of impairment is not limited by the chemical-test rules.^[8][25]

Commercial drivers should also see OWI in a commercial vehicle, and drivers under 21 the zero-tolerance law.