Police don't need a search warrant to draw blood from unconscious people suspected of drunken driving, the U.S. Supreme Court ruled Thursday in a widely watched case from Sheboygan County.

The 5-4 decision featured two opinions on both sides of whether the practice violates the Fourth Amendment right against unreasonable searches.

For the plurality, Justice Samuel Alito called unconscious drivers the most dangerous, and that making police chase down a warrant would take time away from pressing other duties, especially at a crash scene.

And waiting for a judge to approve a search warrant would make the blood test results less reliable, he wrote, joined by Chief Justice John Roberts and Justices Stephen Breyer and Brett Kavanaugh.

Justice Clarence Thomas, in a concurring opinion, wrote that such evidence dissipation alone creates an "exigent circumstance" exception to obtaining a search warrant.

The ruling affirmed Wisconsin's implied consent law, which says that by driving on public roads, drivers agree to be tested for alcohol.

But while a conscious suspect can refuse a breath test or a blood test, which carries its own civil and evidentiary consequences, an unconscious person cannot.

In dissent, Justice Sonia Sotomayor sided with civil libertarians and defense groups that call blood draws one of the most invasive and personal kinds of government searches, and that police can now easily get search warrants electronically and quickly.

"Wisconsin has not once, in any of its briefing before this Court or the state courts, argued that exigent circumstances were present here," Sotomayor wrote.

"In fact, in the state proceedings, Wisconsin 'conceded' that the exigency exception does not justify the warrantless blood draw in this case."

Justices Ruth Bader Ginsburg and Elena Kagan joined the opinion.

Justice Neil Gorsuch dissented separately. He accused the plurality justices of failing to answer the question presented: whether states can bypass the Fourth Amendment's warrant requirement by deeming drivers to have consented to blood draws, even when unconscious.

"Instead, it upholds Wisconsin's law on an entirely different ground — citing the exigent circumstances doctrine."

In May 2013, someone called Sheboygan police to say they had just seen Gerald Mitchell, 55, stumble into a gray minivan and drive off.

About 30 minutes later, police saw Mitchell staggering along the city's Lake Michigan beach, wet and shirtless. He nearly fell over several times, admitted he'd been drinking earlier and that he decided he was too drunk to drive so he parked. Police found the minivan nearby.

He couldn't do field sobriety tests and blew a 0.24 blood alcohol concentration, or BAC, on a preliminary breath test and was arrested for OWI. Preliminary breath test results can't be used as evidence at trial in Wisconsin.

At the jail, he began passing out intermittently, so officers took him to a hospital eight minutes away. By the time they got there, Mitchell was unconscious and could not be roused awake. An officer ordered a blood draw that later showed a 0.22 BAC.

Mitchell tried to suppress the evidence, arguing the blood draw violated his rights, but lost. He was convicted of his seventh OWI offense and sentenced to three years in prison.

Attorney General Josh Kaul welcomed the ruling.

"This law helps protect communities from impaired drivers," Kaul said in a statement.

Interestingly, Thursday's decision actually gives Mitchell one more chance to prove his rights were violated. It vacates the Wisconsin Supreme Court decision affirming Mitchell's conviction and remands the case for a new hearing in Sheboygan County Circuit Court.

"Mitchell may attempt to show that his was an unusual case, in which his blood would not have been drawn had police not been seeking BAC information and police could not have reasonably judged that a warrant application would interfere with other pressing needs or duties," the ruling held.

Contact Bruce Vielmetti at (414) 224-2187 or bvielmetti@jrn.com. Follow him on Twitter at @ProofHearsay.