"17½-year-olds vary widely in their reactions to police questioning, and many can be expected to behave as adults."

So writes Justice O'Connor, concurring and providing the fifth vote, in today's Supreme Court opinion, Yarborough v. Alvarado. The Court leaves in place a state court conviction and reverses the opinion of the Ninth Circuit, which would have required a new trial excluding the statements that were given without Miranda warnings. Under the Antiterrorism and Effective Death Penalty Act of 1996--an omnibus congressional reaction to the Oklahoma City bombing--federal courts can only grant habeas corpus if the state court's decision “was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.” The Supreme Court has cases saying when Miranda warnings are required, but none of them make the defendant's age a factor. The state court only has to get the clear rules of law from the Supreme Court cases right and then not apply them in a way that is unreasonable. The cases in question required police to follow an objective test of whether the person being questioned would feel free to leave. Justice Kennedy, writing for the majority, concentrating on keeping the test objective, thought that "consideration of a suspect’s individual characteristics–including his age–could be viewed as creating a subjective inquiry." Thus, it wasn't "unreasonable" for the state court to fail to make any reference to the defendant's age.

Justice Breyer dissents, joined by Justices Stevens, Souter, and Ginsburg:

Alvarado’s youth is an objective circumstance that was known to the police. It is not a special quality, but rather a widely shared characteristic that generates commonsense conclusions about behavior and perception. To focus on the circumstance of age in a case like this does not complicate the “in custody” inquiry. And to say that courts should ignore widely shared, objective characteristics, like age, on the ground that only a (large) minority of the population possesses them would produce absurd results ....

UPDATE on the theory that some reader somewhere wants some opinion on the subject: This 5-4 split is a very old rift for the Court, which goes back far beyond the 1996 Act that gave the Justices some new terms and some new Congressional intent to take into account. Since at least the mid-70s, the Court has been split over what the role of the federal courts is in habeas cases for state prisoners. To put it simply, one side of the Court views the lower federal courts as having a role similar to the U.S. Supreme Court, making up for the fact that only a very few criminal cases will be heard by the Supreme Court on direct review. They think that the lower federal courts ought to serve as a surrogate for the Supreme Court, redoing the work of the state courts and correcting for mistakes in the articulation and application of law. The other side of the Court thinks that direct review is different from habeas review, and that the lower federal courts, exercising their habeas jurisdiction, should leave state court decisions as the last word unless a particular state court's performance is too far out of line (for example, to use the terms of the 1996 statute, if the state court missed the clear Supreme Court case law or applied it unreasonably). There are very basic differences about federalism here. One side mistrusts the state courts and thinks the federal courts are needed to ensure that there isn't a systematic underenforcement of federal constitutional rights. The other side thinks the state courts basically deserve respect as courts and the role of the federal courts should be to serve as a corrective only when state courts show some sign of not taking its duty to enforce federal law seriously enough. You might think the intrusion of Congress in 1996 into the whole longstanding debate would have resolved this conflict, but, quite interestingly, it hasn't. Congress has the constitutional role to make the statutes that govern federal jurisdiction, but the courts have to interpret those statutes, and the tendency to see in jurisdiction statutes what one thinks federal jurisdiction should be is very strong.