The U.S. Bureau of Justice Statistics has just released a special report on Contacts between Police and the Public in 2005 [313 KB PDF]. Each year, about one in five people in America have an encounter with a police officer, mostly in traffic stops.

There’s lots of interesting information in the BJS’s series of “police and public” reports (like how, in 2005, 83% of people who experienced police use of force thought it was excessive), but the most interesting of all is the data about people giving consent to search. Of the roughly 850,000 police searches in 2005, well over half (57%) were by consent. And in about 10% of those consent searches, the police found criminal evidence.

Why do people consent to police searches, especially people who know the police are going to find criminal evidence? Could it be that they don’t know—or at least don’t truly believe—that they can refuse consent? Could it be that, even if they do know, they don’t know how to and have never had a chance to practice refusing consent (in a role-play, for example)?

The U.S. Supreme Court has said that the police don’t have to tell you that you are allowed to refuse consent to a search. The federal and state governments don’t really spend any money to educate people about their right to refuse consent to a search, either. Even most know-your-rights efforts that do educate people about refusing consent don’t help people practice what it’s like to actually refuse consent (though some do).

Once upon a time, back in 1972, the U.S. Ninth Circuit Court of Appeals said that for a consent to a search to be valid, the police would have to be able to prove that you gave it “with an understanding that it could be freely and effectively withheld.” But the U.S. Supreme Court overruled the Ninth Circuit on that, saying that to require police to tell you that you were allowed to refuse your consent would be “thoroughly impractical.” Justice Thurgood Marshall, dissenting (inspiringly and forcefully, as usual), made this point:

I must conclude, with some reluctance, that when the Court speaks of practicality, what it really is talking of is the continued ability of the police to capitalize on the ignorance of citizens so as to accomplish by subterfuge what they could not achieve by relying only on the knowing relinquishment of constitutional rights.

About a decade earlier, as the Supreme Court was lunging towards its decision in Miranda v. Arizona (which spelled out how the police should read you your rights before questioning you), Justice Arthur Goldberg put an even sharper end on this point:

[N]o system of criminal justice can, or should, survive if it comes to depend for its continued effectiveness on the citizens’ abdication through unawareness of their constitutional rights. . . . If the exercise of constitutional rights will thwart the effectiveness of a system of law enforcement, then there is something very wrong with that system.