Refusing a Breathalyzer or Blood Sample After a DUI Arrest

Refusing to take a test may deprive the prosecution of damning evidence, but it will also usually result in a license suspension. In some situations, a refusal post-arrest can be overcome: a non-consensual blood test may be allowed in rare circumstances.

By , Attorney · UC Berkeley School of Law
Updated August 28, 2021

When a police officer pulls over a motorist suspected of driving under the influence of drugs or alcohol (DUI or DUID), the officer will normally ask the driver to take a blood, breath, or urine test. The purpose of the test is to determine whether drugs and alcohol are present in the driver's body. In most states, drivers who refuse to cooperate face license suspension.

If an officer asks you to perform a breath or other chemical test, should you? The best course of action, of course, depends on the specific circumstances, but there can be serious consequences either way.

DUI Field Sobriety Tests

When you get pulled over on suspicion of driving under the influence, the officer might first ask you to perform a field sobriety test (FST). These FSTs often include walking in a straight line, following with your eyes an object as the officer moves it from side-to-side, and balancing on one foot. Typically, you have the right to refuse to participate in FSTs. In other words, there's no penalty or other legal consequence for refusing to do an FST.

Chemical Testing

Police might also request that a driver who's suspected of drunk or drugged driving take a chemical test. The most common DUI chemical tests are breath and blood tests (urine and saliva tests are some of the less common methods). These tests—blood tests in particular—reveal precisely what substances the driver has in his or her system and in what amounts.

Breath Tests

Breath tests (often called "breathalyzers") measure the amount of alcohol on a person's breath and, based on that measurement, estimate the person's blood alcohol concentration (BAC). There are two types: preliminary alcohol screening (PAS) tests and evidential breath tests (EBTs).

PAS tests (also called "preliminary breath tests" or "PBTs") normally take place at the roadside before police make an actual DUI arrest. Much like with FSTs, drivers typically have the right to refuse a PAS test. Police use PAS tests to detect the presence—not necessarily the exact amount—of alcohol in the driver's system. Generally, PAS machines aren't particularly accurate. So, the results aren't always admissible in court. The results can, however, help police build probable cause to make a DUI arrest. (To make a DUI arrest, police need enough evidence to support a reasonable and objective belief that the defendant was driving under the influence.)

EBTs, on the other hand, normally take place after police arrest a defendant for a DUI. Some EBT machines are small enough for police to carry on patrol. However, the EBT devices used by many law enforcement agencies are large, stationary machines that are kept at the station. The real distinguishing factor between PAS and EBT devices is accuracyEBTs are normally much more accurate than PAS machines. Because of EBT reliability, the results are typically admissible in court to show the amount of alcohol in the driver's system.

Blood Tests

When law enforcement suspects a driver is under the influence of drugs, they'll likely request a blood test. Whereas breath tests are good only for detecting alcohol, blood test results show the amount of drugs and alcohol in the driver's system.

Generally, blood tests are conducted at the police station or hospital.

Refusing to Provide a Sample for a Chemical Test

All states have "implied consent" laws that request drivers who are lawfully arrested to submit to a chemical test when requested to do so by an officer. Drivers who unlawfully refuse testing face license suspension. The suspension period for a test refusal is typically longer than the suspension a driver would receive for a failed test (a BAC of .08% or more in most states) or a DUI conviction.

Some drivers might refuse testing to avoid being convicted of a DUI. Without test results, the prosecution won't have evidence of exactly what the motorist ingested prior to driving. However, the prosecution can generally inform the jury about the defendant's refusal and argue that the defendant likely did so to conceal intoxication. So, a driver can still be convicted of a DUI; chemical test results aren't strictly necessary.

Refusing a Chemical Test as a Legal Strategy

In some circumstances, a driver might be better off refusing a chemical test. Generally, a refusal will lead to license suspension but make it more difficult for the prosecution to prove the DUI charge in court. However, whether refusing a chemical test is advisable depends on many facts, including state-specific laws and the driver's level of impairment. And the reality is that most people don't have the legal expertise necessary to make the right call. If you're curious about this issue, it's best to talk with an experienced DUI attorney.

Forced Blood Samples

Previously, in any case where DUI was suspected, officers in some police departments would take a blood sample for chemical testing without the driver's consent and without a warrant. In Missouri v. McNeely, 133 S. Ct. 1552 (2013), the Supreme Court concluded that that officers cannot routinely take forced blood samples in all suspected DUI cases, and that taking a blood sample without a warrant cannot be justified merely because alcohol dissipates rather quickly over time. Rather, the situation must be considered on a case-by-case basis and officers can take a blood sample without a warrant and without a person's consent only if there are special facts that make it necessary to do a blood draw before too much time passes and the alcohol in the driver's blood dissipates. For example, if a driver has been seriously injured, and the officer needs to do the blood draw immediately before transporting the driver to the hospital for medical treatment, then an officer can do a blood draw without a driver's consent.

Getting Legal Advice and Representation

In most states, a driver is not permitted to talk to an attorney before deciding whether to provide a sample for a chemical test and what kind of test to take. As you have learned, states can impose serious consequences when drivers refuse to cooperate. If you are charged with a DUI, you will benefit from having an experienced attorney explain the laws in your state and how the case is likely to be treated in your community. Some consequences may be unavoidable, such as a driver's license suspension, but you will still benefit from the advice of an attorney.

Refusal to Take Tests: State Implied Consent Laws

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