If you are stopped by the police in the US are you allowed to refuse any test to prove your sobriety? I know you have to tell the police your name, provide them with identification, insurance, and driver's license but can you refuse to give them anything else? Or is this just handing them probable cause on a silver platter?

  • 1
    State regulated Jul 31, 2021 at 20:37
  • @GeorgeWhite Agree that there are material differences from state to state. There is not a federal right to refuse without consequences.
    – ohwilleke
    Aug 2, 2021 at 21:04

2 Answers 2


In the circumstance you describe, you can refuse a breathalyzer test ("opt to not take it"), and doing so would not constitute probable cause for an arrest (the results of the test can be probable cause). That is when you are on the roadside. This is Washington's "implied consent" law. One of the first things that the law says is that the test is "subject to the provisions of RCW 46.61.506", which includes the requirement that the test be performed

according to methods approved by the state toxicologist and by an individual possessing a valid permit issued by the state toxicologist for this purpose. The state toxicologist is directed to approve satisfactory techniques or methods, to supervise the examination of individuals to ascertain their qualifications and competence to conduct such analyses, and to issue permits which shall be subject to termination or revocation at the discretion of the state toxicologist.

There are other requirements regarding 15 minute prior observation. The legally required test is done in the police station by a specially trained technician, on an approved machine (the portable machine is not approved). The implied consent law also says that this test is "required"

if arrested for any offense where, at the time of the arrest, the arresting officer has reasonable grounds to believe the person had been driving or was in actual physical control of a motor vehicle while under the influence of intoxicating liquor

You are not required to take the Portable Breath Test, which is optional (when you have been stopped) – it's the post-arrest "evidentiary" test that is obligatory, using the approved procedure. Note that failing the optional test gives probable cause for an arrest, however there can be other grounds such as failing the line-walking test. If the officer just tells you that the roadside test is mandatory, that is a defense which can be used at trial ('cuz the optional test is not mandatory). Whether or not the portable test is admissible in court depends on the state: in Kentucky it is statutorily not admissible, likewise in Washington per court ruling.

The other tests (often known as Standard Field Sobriety Test) are also optional, so ultimately it reduces to whether they already have probable cause, that is, if "the totality of the facts and circumstances known to the officers at the time of arrest would warrant a reasonably cautious person to believe a crime has been committed". It is just not clear to me what actual circumstances distinguish mere reasonable suspicion (driving slow) from probable cause, but watery eyes, slurred speech and alcohol smell will make probable cause. I don't know if driving slow and having watery eyes is probable cause – I would think not. Dunno about "smell of alcohol plus driving slow".

In Birchfield v. North Dakota, 579 US ___ we find an example of a traffic stop with ample probable cause for an arrest (smell of alcohol, bloodshot watery eyes, driving into a ditch, failing the alphabet test and massively failing the voluntary breath test). The analogous North Dakota law is largely similar to Washington law, mandating only the "approved" more technical version of the test and not the roadside test. Defendant, in that case, refused the mandatory test. A crucial difference compared to Washington law is that while suspension of driving privileges follows from refusal under Washington law, refusal in North Dakota is itself a misdemeanor per N.D.C.C. § 39-08-01. The issue for SCOTUS is whether a law criminalizing refusal to submit to a breath test (but not a blood test) violates the 4th amendment: it does not.

  • Is the straight line test mandatory? Is the following question. I can ask it in a separate question if you think it better to do so.
    – Neil Meyer
    Jul 30, 2021 at 23:34
  • OK, I did not realise there is more than one type of breathalizer test. When I said breathalyser I meant the mobile one. I will edit m question to be more specific
    – Neil Meyer
    Aug 25, 2021 at 16:31

It depends. According to Birchfield v. North Dakota, 136 S. Ct. 2160 - Supreme Court 2016 (emphasis mine):

Because the impact of breath tests on privacy is slight, and the need for BAC testing is great, the Fourth Amendment permits warrantless breath tests incident to arrests for drunk driving. Blood tests, however, are significantly more intrusive, and their reasonableness must be judged in light of the availability of the less invasive alternative of a breath test. Respondents have offered no satisfactory justification for demanding the more intrusive alternative without a warrant. In instances where blood tests might be preferable — e.g., where substances other than alcohol impair the driver's ability to operate a car safely, or where the subject is unconscious — nothing prevents the police from seeking a warrant or from relying on the exigent circumstances exception if it applies. Because breath tests are significantly less intrusive than blood tests and in most cases amply serve law enforcement interests, a breath test, but not a blood test, may be administered as a search incident to a lawful arrest for drunk driving. No warrant is needed in this situation.

So it seems like it depends on:

  • Whether the police have a warrant.
  • Whether the police have enough evidence to make an arrest, and can thus perform a breath test incident to the arrest.
  • Whether the police have some other valid exception to the warrant rule.
  • Whether the police are demanding a blood test or a breath test.
  • What you consider "allowed" to include. In some states, you can technically refuse in some circumstances, but your refusal can come with penalties, like your license gets revoked, and the refusal may be used against you in a criminal prosecution.
  • The law in your state.

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