There seemed little enthusiasm among the justices for that categorical approach. Instead, the argument turned into a search for a middle ground that would take account of the practical realities of roadside stops, body chemistry and the administration of justice in the digital age.
On the one hand, the natural dissipation of blood alcohol means that time is of the essence when people suspected of drunken driving are pulled over and refuse to consent to a breath test. Obtaining a warrant, moreover, takes time.
On the other hand, several justices expressed discomfort with what Chief Justice John G. Roberts Jr. called the “pretty scary image” of government-sanctioned bodily intrusions involving sharp needles.
The case arose from the arrest of Tyler G. McNeely, who was pulled over for speeding on a Missouri highway and exhibited, the State Supreme Court said, “the telltale signs of intoxication — bloodshot eyes, slurred speech and the smell of alcohol on his breath.” He performed poorly on a field sobriety test and was arrested.
Mr. McNeely refused to take a breath test or, after being taken to a hospital, to consent to a blood test. One was performed anyway, about 25 minutes after he was pulled over, and it showed a blood alcohol level of 0.15 percent, almost twice the legal limit.
The state court suppressed the evidence, saying there had been no “exigent circumstances” that excused the failure to obtain a warrant. “Warrantless intrusions of the body are not to be undertaken lightly,” the court said in an unsigned opinion.
In 1966, in Schmerber v. California, the United States Supreme Court said no warrant was required to take blood without the driver’s consent after an accident in which the driver and a passenger were injured. The fact that alcohol levels diminish over time figured in the court’s analysis, as did the time it took to investigate the scene of the accident and move the injured people to the hospital.
The question in the case heard Wednesday, Missouri v. McNeely, No. 11-1425, was whether the dissipation of blood alcohol by itself justifies taking blood without a warrant when there are no additional factors complicating matters.
Much of the argument concerned how long obtaining a warrant actually takes these days and whether the Supreme Court should encourage streamlined procedures. In some places, the justices were told, warrants can be obtained by phone in as little as 15 or 20 minutes; in others, the process can take two hours or longer.
Nicole A. Saharsky, a lawyer for the federal government, said the day might come when warrants could be obtained so quickly that courts should perhaps require them. “If the world changed,” she told the justices, “so that every police officer had an iPad and that judges were always on duty and that the warrants could be gotten that quickly, you would consider that.” But she said that was not the reality in most of the country today.
That concession, Justice Antonin Scalia said, supported a case-by-case approach. “If it would have taken too long, then it’s O.K. without a warrant,” he said. “If it wouldn’t have taken that long, it’s bad.”
Later, though, Justice Scalia asked Steven R. Shapiro of the American Civil Liberties Union, which represents Mr. McNeely, whether warrants played an important role in stopping unreasonable searches if they were quickly and routinely available.
Mr. Shapiro responded that “the privacy safeguards of the Fourth Amendment benefit by having a neutral and detached magistrate review the evidence before the state does something as intrusive as putting a needle in somebody’s arm.”
The justices also explored other ways of obtaining the required evidence.
“Breathalyzers in my mind have a much different intrusion level,” Justice Sonia Sotomayor said. “They don’t intrude into your body.”
But John N. Koester Jr., a lawyer for Missouri, explained that “it’s very difficult for practical reasons to force someone to blow into the Breathalyzer.”
“You have to take a very deep breath,” he said. “And one police officer told me it’s sort of like you can put a balloon in front of somebody’s mouth, but you can’t make him blow it up.”
Justice Scalia later proposed a second idea: that drivers “in a paddy wagon and on the way to the hospital” could be told a warrant had been requested and that, one way or the other, blood would be drawn unless they agreed to a breath test.
Ms. Saharsky said such drivers might nonetheless “take their chances that the evidence is going to dissipate.”
Justice Elena Kagan said it was also possible that the drivers would not make rational calculations.
“Maybe they’re drunk,” she said.
