The Supreme Court takes on collective punishment.

You would think the following scene occurs every day: Cops pull over a speeding vehicle and search for drugs. Crack is found. All three passengers insist the drugs are not theirs. So the cops arrest them all. The constitutional dispute today is whether the cops had probable cause to arrest everybody, or just the driver, or just the guy next to the wad of bills in the glove compartment, or just the guy in the back seat with the crack. All of which is interesting. But even more interesting is that this is a case of "first impression" for the high court—meaning no one has brought this kind of challenge before. Apparently, in every other car ever stopped, someone has cheerfully admitted to owning the drugs.

Joseph Pringle made several mistakes on Aug. 7, 1999. One was being the passenger in a car with a driver who consented to a police search. Another was hiding the big wad of $763 in cash in the glove box of that car—where the license and registration lived. Another was hiding the five baggies of crack cocaine in the back seat, cleverly jammed behind the armrest. Another was later confessing at the police station that yes, the drugs were his and that he was hoping to trade them for sex at a party (I always find that "Nice dress" or "Great party, huh?" works OK, too).

At his suppression hearing, Pringle argued that even though he'd confessed to everything, the cops should not have been allowed to arrest him in the first place because under the Fourth Amendment they did not have sufficiently particularized suspicion that the drugs were his. The Maryland Court of Appeals agreed with him, holding 4-3 that since Pringle was in the front passenger seat and the drugs were stashed in the rear armrest, there was no probable cause to arrest him. The state of Maryland appealed.

Gary E. Bair argues for Maryland this morning, and Bair seems to believe that the state has probable cause to arrest everyone in a drug-mobile because it's always a reasonable assumption that they all know about the drugs. Bair apparently lives in the Land That Knows No Carpools. And he thus spends most of his time this morning resisting the planes, trains, and automobiles hypotheticals put forth by the justices.

What if the drugs had been found closer to the driver, rather than in the back seat, asks Sandra Day O'Connor. Could all three passengers still be arrested? Yes, says Bair, because the car is a common area. What if the drugs were found in the trunk, asks Ruth Bader Ginsburg. Well, says Bair, if there were a "large quantity of drugs in the trunk, or a dead body in the trunk …"; Ginsburg reminds him that this is her hypo and there is just a Ziploc bag in the trunk, not a dead body.

Then it's O'Connor's turn with the innocent-grandma hypo: "What if it's a high-crime area and some mother gets a ride from her son and doesn't know he's involved with drugs?" Can she be arrested? "Supposing it's the middle of the day," she adds. "And she's going to the grocery store?" Bair can't quite make himself say "Lock the old drug-mom up." So he mumbles something about a "totality of the circumstances test."

Justice John Paul Stevens has a hypo, too. What if there were four passengers in the car instead of three? No different says Bair. "What if there were six?" asks Stevens. Same. Stevens, undaunted: "What if it's a minivan and there are eight people?" he asks. Lock 'em up. Stevens takes a breather while Ginsburg takes over: "What if it had been a bus?"

Bair seems ready to concede that he would not seek to arrest all the passengers on a bus just because someone had drugs. Prompting Antonin Scalia to enter the bidding war to ask if the result would be different if it were a public bus or a charter bus. He appears to be asking this question purely for recreational purposes.

Anthony Kennedy wonders whether the police, upon finding a dead body and two possible killers, each claiming the other did it, could arrest them both. Bair, who couldn't get Ginsburg on board with his dead body in the trunk hypo, appears relieved that the corpses are back. He says both potential killers could be subject to arrest.

Stevens then notes that there are three suspects here—not two. So it's not as if there's a 50 percent chance that one guy is the criminal. There's only a 33.3 percent chance. Can a mere 33.3 percent likelihood of criminality constitute probable cause? Bair insists you cannot quantify probable cause. Stevens is unperturbed. So what if there are four people and each is only 25 percent likely to be the criminal?