By Lawrence Hurley and Andrew Chung
WASHINGTON (Reuters) - U.S. Supreme Court justices on Tuesday wrestled with whether police need a court-issued warrant to draw an unconscious suspect's blood in a case involving a Wisconsin man convicted of drunken driving based on blood obtained without his consent.
The nine justices appeared divided over the case as they heard about an hour of arguments in an appeal by the man, Gerald Mitchell, of state court rulings that endorsed the ability of police to test blood drawn from an unconscious person.
Mitchell appealed a ruling by Wisconsin's highest court that the blood draw did not violate the U.S. Constitution's Fourth Amendment protections against unreasonable searches. Police drew the blood, which showed his blood-alcohol concentration far above the state's legal limit, after finding Mitchell shirtless, wet and covered in sand near the shores of Lake Michigan.
At issue is a Wisconsin law that assumes motorists automatically give consent to tests of their breath or blood simply by driving on the state's roads, even if they are unconscious. More than half the 50 U.S. states have similar laws.
Chief Justice John Roberts and Justice Samuel Alito, both conservatives, appeared sympathetic to Wisconsin.
"Ignorance of the law is no excuse," Roberts said, invoking a old legal maxim. "Why do you need them to sign a piece of paper?"
Alito noted that agreeing to a blood draw could be viewed as "a condition to the privilege of driving" on Wisconsin's roads.
Liberal justices appeared to sympathize with Mitchell. Justice Sonia Sotomayor said although motorists generally know that driving under the influence is illegal, whether they are aware blood can be drawn without consent is a different issue.
"This is not quite ignorance of the law. This is something substantially different because you're talking about ... knowledge that your body can be invaded by police to secure evidence to prove you drove intoxicated," Sotomayor said.
Fellow liberal Justice Elena Kagan said a law like Wisconsin's works fine when drivers are conscious because they can withdraw consent when police ask for a blood draw.
"But that falls apart in this situation of the unconscious driver," Kagan added.
The Supreme Court in recent years has limited police ability to draw blood without a warrant and without a motorist's consent, and frowned upon criminal penalties against people who refuse to consent to a blood draw.
The case dates to 2013 in Wisconsin's Sheboygan County when Mitchell's neighbor called police to report that Mitchell had driven away in a van, apparently drunk, and may have been suicidal. He had taken about 40 pills along with vodka mixed with the soft drink Mountain Dew, according to court filings. Mitchell later testified he had been depressed and suicidal.
After police found him, Mitchell fell unconscious as authorities drove him to a hospital, where they ordered staff to draw his blood for an alcohol concentration test despite not having a warrant. Police charged him with operating a vehicle while intoxicated.
A ruling is due by the end of June.
(Reporting by Lawrence Hurley and Andrew Chung; Editing by Will Dunham)