The Minnesota Supreme Court ruled Wednesday that collecting urine without a warrant in suspected drunken driving cases is unconstitutional, mirroring earlier findings from the U.S. Supreme Court regarding blood tests.

“Such tests significantly intrude upon an individual’s privacy and cannot be justified by the State’s interests given the availability of less-invasive breath tests that may be performed incident to a valid arrest,” Chief Justice Lorie Gildea wrote in the court’s opinion in State v. Thompson.

The American Civil Liberties Union of Minnesota applauded the decision.

“Forcing Minnesotans to undergo an intrusive blood or urine search without a warrant, violates fundamental privacy rights,” its executive director, Charles Samuelson, said in a written statement.

Ryan M. Thompson was arrested in April 2012 for suspected drunken driving. He failed field sobriety tests and a preliminary breath test, and refused to provide a blood or urine test in jail.

Thompson was charged with refusing the tests, and convicted. The conviction was overturned by the Court of Appeals, which ruled that Thompson’s rights had been violated because a warrant had not been issued for either his blood or urine. The state argued that Minnesota law was constitutionally applied in Thompson’s prosecution.

The U.S. Supreme Court’s decision in Birchfield v. North Dakota that found warrantless blood tests were unconstitutional because of the physical intrusion caused by inserting a needle into a defendant’s body served as a framework for testing Minnesota’s law, according to the state Supreme Court. The federal decision did not address warrantless urine tests.

Gildea wrote that although urine tests don’t require physical intrusion into the body, as Thompson argued, there is an even greater risk associated with urine samples, as they can “contain additional metabolites and other types of ‘highly personal information’ that will never appear in a blood sample.”

Unlike breath tests, Gildea wrote, urine tests can be used to determine a host of medical conditions, including pregnancy, diabetes and epilepsy. She added that defendants must urinate in full view of the arresting officer.

“Compared to blood testing, which does not involve an arrestee performing a private bodily function in front of law enforcement, urine testing involves a greater invasion of privacy in terms of embarrassment,” she wrote.

Attorney Dan Koewler, who argued the Thompson case before the state Supreme Court, said that police can no longer demand that suspected drunken drivers urinate in front of them although breath tests can still be requested.

William Lemons, who represented the Minnesota County Attorneys Association and League of Minnesota Cities, said he expects to see little impact on public safety. The move to electronic warrants should make it easier for police and judges to get the warrants, he said.

It’s unclear what will happen if suspects refuse a test after a warrant has been issued, Koewler said, adding that law enforcement could use a forced blood draw to compel compliance. In South Dakota, he said, some cases have involved forced use of catheters.

The state Supreme Court also found it unconstitutional to charge someone for refusing a blood or urine test.