A three-judge panel of the Minnesota Court of Appeals on Monday threw out the conviction of a Minnesota man who refused to submit to a urine test after he was stopped by police on suspicion of drunken driving.

The appellate court ruled that police needed a warrant if they wanted a sample of Ryan Mark Thompson's urine to prove he was driving drunk.

Thompson, 41, of Owatonna, was arrested in April 2012 on suspicion of driving under the influence.

He was charged with second-degree test refusal, third-degree driving while under the influence, obstructing the legal process and driving over the centerline.

After all other charges were dropped, Thompson was convicted of refusing a urine test. He challenged the constitutionality of the test-refusal law, saying it violated his due-process rights.

Thompson's case is one of several that challenge Minnesota's test-refusal law. Two weeks ago, the U.S. Supreme Court agreed to review Minnesota's unique law, which makes it a crime for a suspected drunken driver to refuse a warrantless breath, blood or urine test.

In its ruling Monday, the state Court of Appeals said that "conducting a warrantless blood or urine test" on Thompson "would not have been constitutional" because it "implicates his fundamental right to be free from unconstitutional searches."

Thompson's attorney, Charles Ramsay of Roseville, said Monday that he was "very happy" that Thompson's conviction was vacated.

"Right now, Mr. Thompson is an innocent man," he said.

What remains to be seen is what impact the ruling — and the U.S. Supreme Court's upcoming review — will have on the law overall.

A message left with the Steele County attorney's office was not immediately returned Monday afternoon.

Oral arguments in the case under Supreme Court review — State vs. Bernard — will be made by local attorney Jeff Sheridan and a Washington, D.C., law firm. Sheridan has argued since 2002 that the state's implied-consent law is unconstitutional. Appellate courts have issued disjointed rulings on whether a warrant should be required to administer a breath, blood or urine test, he said, adding that he believes a DWI shouldn't be treated differently from any other crime.

Ramsay agrees, and plans to offer a written brief in support of Sheridan's case.

Most states, Ramsay said, consider requiring a defendant to submit to blood or urine testing without a warrant to be an unconstitutional breach of a defendant's right to be free from unreasonable searches — or from incriminating themselves.

"I think that in most states, it is quite simple," Ramsay said. "But Minnesota has made it difficult."

The U.S. Supreme Court has ruled that taking blood and urine samples is a "search" under the Fourth Amendment and therefore requires a warrant.

But the Minnesota Supreme Court ruled in February that such warrantless searches do not violate the state and U.S. Constitutions.

As a result, in Minnesota, a suspected drunken driver can still be charged with refusing a breath or blood test if police believe there's enough evidence to get a search warrant to require the test — even if they don't obtain the warrant. Only a few states have a similar implied-consent law.

In November, the Court of Appeals ruled that a warrantless blood test was "undeniably intrusive," leaving only the issue of warrantless urine tests. According to Monday's ruling, those tests also are unconstitutional.

"A urine test is unquestionably more intrusive than a breath test," Judge John Smith wrote in support of the opinion.

Case background

In April 2012, an Owatonna police officer sitting outside a bar at closing time saw a car driven by Thompson jump a curb, stop quickly and then drive over the centerline after exiting the bar parking lot.

According to court documents, the officer, after stopping Thompson, "detected an overwhelming odor of an alcoholic beverage coming from the vehicle" and "noticed that Thompson 'had watery and glassy eyes.' Thompson stated that he had consumed one beer." The officer then asked Thompson to submit to field sobriety tests, which Thompson failed. Thompson also "failed a preliminary breath test."

Thompson was arrested. He refused to take a blood or urine test.

The district court concluded that the test-refusal statute is constitutional before Thompson appealed.

Staff writer David Chanen contributed to this report.

James Walsh • 651-925-5041