Before or after a person’s arrest for a DUI/DWI criminal offense, police officers may ask the accused/defendant to submit to a breath test for alcohol concentration 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 (.05 in Utah). A breath test measures the amount of alcohol in the air a person exhales and uses that amount to estimate how much alcohol is in the person’s blood (BAC).

There are two types of breath tests: (1) a portable breath test (PBT) that is typically given in the field (at the side of the road or other place where a driver has been detained); and (2) the Intoxilyzer or DataMaster breathalyzer machine that is usually located at the police station. The results of a PBT are generally not admissible at trial but may be the basis for probable cause for the police officer to arrest a driver when the test shows a BAC of .08 or higher in most states (.05 in Utah). And the results of an Intoxilyzer test generally are admissible at trial.

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 breath or blood test there are other consequences even if the police do not secure a search warrant for a blood draw—including fines, penalties, and automatic suspension of the driver’s license for a year or more.

In Texas, the legal limit for blood alcohol concentration (BAC) is 0.08 for drivers 21 years and older, and any level of detectable alcohol for drivers under 21. Police officers may request a breath test before or after an arrest for DUI/DWI to determine if a person is per se intoxicated. There are two types of breath tests used in Texas: the portable breath test (PBT) and the Intoxilyzer. PBT results are typically used to establish probable cause for arrest and are not generally admissible in court, while Intoxilyzer results can be used as evidence at trial. Texas has implied consent laws, meaning that by accepting a driver's license, drivers have consented to submit to chemical tests if lawfully requested by an officer. Refusal to take a breath or blood test can result in consequences such as fines, penalties, and automatic suspension of the driver's license. Following the U.S. Supreme Court's rulings, forced blood draws without consent require a search warrant unless the individual is unconscious and there are exigent circumstances justifying the draw without a warrant.