According to a study last year by William M. Landes, who teaches law and economics at the University of Chicago, and Judge Richard A. Posner of the federal appeals court there, four of the five most conservative justices to serve on the court since 1937, of a total of 43, are on the court right now: Chief Justice John G. Roberts Jr. and Justices Scalia, Clarence Thomas and Samuel A. Alito Jr. The fifth was Chief Justice William H. Rehnquist, whom Chief Justice Roberts replaced in 2005.

The study took into account the votes in divided cases on ideologically charged issues like criminal procedure, civil rights and the First Amendment. Justice Thomas, the most conservative justice in the study, voted for the conservative position in those cases 82 percent of the time. Justice Marshall, the only other African-American to serve on the court, was by this measure the most liberal, voting for the conservative side 21 percent of the time.

The study also reinforced Justice Stevens’s caveat, counting Justice Ginsburg as more liberal than the justice she replaced, Justice Byron R. White. But Justice Ginsburg, whom the study identifies as the most liberal current justice, barely makes the Top 10 in the full tally.

The Roberts court is, then, conservative by the standards of recent history. But is it conservative in some absolute sense?

“It is fair to say that the Supreme Court both now and historically has been to the left of the American public,” said Nathaniel Persily, a law professor at Columbia and an editor of “Public Opinion and Constitutional Controversy” (Oxford, 2008).

“On school prayer, for instance, the Supreme Court is far to the left of the American public,” Professor Persily said, referring to decisions saying that officials may not organize, lead or endorse prayer or devotional Bible reading in the public schools.

“On racial issues, it’s pretty clear from the Michigan cases that the Supreme Court is out of step with the American public,” Professor Persily said of the pair of 2003 decisions allowing public universities to consider race in admissions decisions. (In a 2007 decision, the Roberts court leaned the other way, forbidding public school systems from explicitly taking race into account to achieve or maintain integration.)