The court said it will decide if police who want to look for drugs or evidence of other crimes must first must inform public transportation passengers of their legal rights. The ruling could clarify what police may and may not do as they approach and search a passenger.
Buses and trains are sometimes used by drug couriers. Airplanes are also commonly used to transport drugs, although it is not clear whether the Supreme Court's ruling would apply to plane passengers.
Without mentioning the Sept. 11 jetliner hijackings specifically, the Bush administration invoked the war on terrorism and the concern over airplane security in trying to persuade the high court to take the case.
"Programs that rely on consensual interactions between police officers and citizens on means of public transportation are an important part of the national effort to combat the flow of illegal narcotics and weapons," Solicitor General Theodore Olson wrote.
"In the current environment, they may also become an important part of preventing other forms of criminal activity that involve travel on the nation's system of public transportation," Olson wrote.
The high court previously ruled that police may not squeeze sealed luggage to hunt for drugs, and also said that police questioning aboard buses is not necessarily more coercive just because a passenger may have little room to move about.
The Supreme Court agreed to hear the federal government argument that police officers in Tallahassee, Fla., were within their rights as they questioned and searched two men aboard a Greyhound bus in 1999.
Three officers boarded the bus, bound from Fort Lauderdale to Detroit. One officer knelt backward in the driver's seat, facing the passengers. The other two worked their way from the back of the bus forward, asking passengers about their travel plans and about their luggage.
An officer introduced himself to Christopher Drayton and Clifton Brown, and told them he was looking for illegal drugs and weapons. Drayton and Brown agreed to let officers search a bag in the overhead luggage rack, and it yielded no drugs or weapons.
Police then asked to pat down the men's baggy clothing. The men agreed, and officers felt hard objects on the men's legs that turned out to be packets of cocaine.
Both men were convicted and sentenced on drug charges.
On appeal, the 11th U.S. Circuit Court of Appeals ruled the cocaine should not have been admitted as evidence, because the officers failed to tell the men they were not required to cooperate, or otherwise inform them of their rights.
The encounter violated the Constitution's ban on unreasonable searches and seizures, in part because the men did not feel free to leave, the court said.
In his appeal to the Supreme Court, Olson said that appealcourt decision threatens a common law enforcement tactic, and conflicts with other federal appeals courts.
The confusion has left federal, state and local law enforcement officers "without clear guidance on the boundaries of lawful bus, train and airplane interdiction practices," the government lawyer wrote.
Lawyers for Drayton and Brown urged the Supreme Court to stay out of the case.
The lower court decision, "which merely required compliance with the Constitution and precedent of this court, was a sound application of well-established law," the lawyers for the two men argued. "Nothing in our recent national tragedies changed that."
The case is United States v. Drayton, 01-631.
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