Following a person’s arrest for a DUI/DWI criminal offense, police officers will ask the accused/defendant to submit to a blood test or blood draw in which a qualified person such as a nurse at the police station or hospital will draw the defendant’s blood (usually from the arm) into a vial to be tested for alcohol concentration and ultimately to determine whether the person is per se intoxicated. Per se intoxication is intoxication by definition—as defined in the state’s statutes, which is often a blood alcohol concentration (BAC) of .08 or higher.

All states have implied consent laws that make a driver’s consent or agreement to submit to a blood, breath, or urine test (a chemical test) when requested by a law enforcement officer a condition of the driver’s acceptance of a driver’s license offered by the state. Despite implied consent laws, in 2013 the United States Supreme Court held that if a person refuses to submit to having their blood drawn the police cannot draw the blood by force without a search warrant, as required under the Fourth Amendment to the United States Constitution. But more recently the Supreme Court upheld a nonconsensual blood draw of an unconscious person suspected of driving under the influence—based on the state’s implied consent laws and the exigent circumstances exception to the Fourth Amendment's warrant requirement.

And if a driver refuses to take a blood or breath test there are other consequences even if the police do not secure a search warrant for the blood draw—including admission of the refusal in evidence at trial, fines, penalties, and automatic suspension of the driver’s license for a year or more.

In Oregon, as in all states, implied consent laws require drivers to submit to chemical tests (blood, breath, or urine) if they are arrested for a DUI/DWI offense. Oregon's implied consent law means that by driving on Oregon roads, drivers have consented to these tests if they are arrested for DUI/DWI. The legal limit for blood alcohol concentration (BAC) in Oregon is .08%, and reaching or exceeding this limit can lead to a per se intoxication charge. Following the 2013 U.S. Supreme Court decision, police officers in Oregon cannot forcibly draw blood without a search warrant if a person refuses to submit to a blood test, except in certain circumstances such as when the driver is unconscious and exigent circumstances are present. Refusing a chemical test in Oregon can result in consequences independent of criminal DUI/DWI charges, including the admission of the refusal as evidence in court, fines, penalties, and an automatic driver's license suspension for at least one year.