"Excuse me, do you mind if I take a look inside your bag?"
It may not sound like an effective law-enforcement technique, but the surprising thing is how often criminals are nabbed through such voluntary, warrantless searches.
The reason: Most people don't know they have a right to refuse a police request to search their bags or body. Even those who are aware of their privacy rights may nonetheless be reluctant to tell an earnest police officer to take a hike.
That's why some privacy advocates say law-enforcement officials should be required to advise their targets that they have a right to just say no to a warrantless police search in a public place.
Monday, the US Supreme Court rejected this approach and instead ruled that such warnings are not required by the Fourth Amendment.
In a case with potential major implications for the war on terrorism, the nation's highest court has given a green light to police officers seeking to use the persuasive force of their badge, rather than a judicially approved warrant, to help catch criminals.
A person's ignorance of the constitutional right to refuse a police request for cooperation is not a defense in the face of such dragnet tactics, the high court said in a 6-to-3 decision.
"The court has rejected ... the suggestion that police officers must always inform citizens of their right to refuse when seeking permission to conduct a warrantless consent search," writes Justice Anthony Kennedy for the majority. "While knowledge of the right to refuse consent is one factor to be taken into account, the government need not establish such knowledge as the sine qua non of an effective consent."
The decision comes in a case involving two men, Christopher Drayton and Clifton Brown, convicted of drug trafficking after a random police search of bus riders located narcotics under their clothes. An appeals court threw out the convictions because the men weren't told beforehand that they didn't have to cooperate.
In reversing this ruling, the high court said there is no per se rule requiring that officers must always advise bus passengers of their right not to cooperate. The key issue, according to the majority, is whether, given the totality of the circumstances, a reasonable person would feel free to refuse to cooperate.
In a dissent, Justice David Souter said it was hard to imagine that Mr. Drayton or Mr. Brown believed they had any free choice to ignore the police request to search them. "No reasonable passenger could have believed that, only an uncomprehending one," he writes.
The decision is the most recent in a string of judicial rulings concerning bus-interdiction operations run by law-enforcement officials in Florida seeking to crack down on the use of long-distance bus routes to smuggle narcotics.
But the ruling may prove even more useful for counterterrorism agents. It comes at a time when top government officials, including the FBI director, are warning that the US may soon be subjected to the same kind of suicide bombings on buses and in other public areas as experienced in Israel.
The decision applies to police operations on all public-transportation systems, including airplanes, trains, and subways, as well as in airports and on city streets. In addition, it applies to law-enforcement officials searching for weapons and explosives.