By Linda Greenhouse
New York Times
WASHINGTON – The Supreme Court this week endorsed the use of police roadblocks as an investigational tool for finding witnesses to recent crimes.

Overturning a ruling by the Illinois Supreme Court, which found the tactic unconstitutional in the absence of a reason to suspect a given motorist of involvement in a crime, the justices held that a properly established "information-seeking checkpoint" was a valid way for the police to enlist the public's assistance.

All nine justices agreed that the roadblocks could be constitutional, depending on the circumstances. They divided 6 to 3, though, in appraising the roadblock in this case.

The police in Lombard, Ill., a Chicago suburb, set it up on a highway where exactly one week earlier a hit-and-run driver killed a bicyclist. The police stopped drivers for 10 to 15 seconds each to ask if they had any knowledge of the accident. One man who was arrested at the roadblock for drunken driving brought the constitutional challenge that led to the Supreme Court case.

The majority opinion by Justice Stephen G. Breyer held that given the "grave" public concern about a fatal accident, this roadblock was well planned, minimally intrusive and constitutionally reasonable. Three other justices, though, said they did not have enough information to draw that ultimate conclusion.

Justices John Paul Stevens, David H. Souter and Ruth Bader Ginsburg said the Illinois courts should review the case again and pursue such questions as, for example, whether the police had a basis for believing that the roadblock would be more effective at finding witnesses than leaflets placed on the cars of employees who worked nearby and who might have been changing shifts at the time of the accident. The Illinois Supreme Court did not inquire into the circumstances of the Lombard roadblock because it concluded that such roadblocks were unconstitutional regardless of circumstances.

The State Supreme Court had based that conclusion on a roadblock case from Indianapolis that the justices decided in 2000. In that case, Indianapolis v. Edmond, the court found unconstitutional a roadblock at which the police walked around cars with a drug-sniffing dog, seeking evidence of drug crimes. The justices found that the police lacked "individualized suspicion" that the drivers they stopped might be engaged in crime. Without such suspicion, the roadblock was an unreasonable seizure under the Fourth Amendment, the court said then.

In the case on Tuesday, Illinois v. Lidster, No. 02-1060, Justice Breyer said the informational roadblock differed significantly from the drug-detection roadblock the court considered earlier. "The stop's primary law enforcement purpose was not to determine whether a vehicle's occupants were committing a crime," he said, "but to ask vehicle occupants, as members of the public, for their help in providing information about a crime in all likelihood committed by others."

Justice Breyer added that "the law ordinarily permits police to seek the voluntary cooperation of members of the public in the investigation of a crime." At another point in the opinion, noting that the court's precedents permitted sobriety checkpoints and roadblocks at the country's borders, he observed: "The Fourth Amendment does not treat a motorist's car as his castle."

When the case was argued in November, Justice Breyer made it clear that he regarded the roadblock as only a minimal inconvenience, little different from an ordinary traffic tie-up. He noted that he had been delayed a few minutes by roadside tree-trimming on his way to the court that morning.

The man who challenged the roadblock's constitutionality, Robert Lidster, was arrested after he swerved when approaching the roadblock and nearly hit one of the officers. He failed a sobriety test and was convicted of drunken driving, a conviction that the state appellate courts overturned.

The roadblock led only indirectly to catching the hit-and-run driver whom the police were seeking. Television coverage of the roadblock prompted a viewer to call the police and identify a suspect.