Over at Faculty Lounge, Eric Muller has a post on Justice Sotomayor’s debut opinion in Mohawk Industries, Inc. v. Carpenter, noting Justice Thomas’s concurrence in part and in the judgment, and stating that “The Rehnquist Court tradition was to give a new Justice a unanimous opinion for his or her first assignment.” And he notes a Washington Post article covering Justice Alito’s first opinion stating: “Following Supreme Court tradition for new justices, Chief Justice John G. Roberts Jr. assigned Alito a unanimous opinion as his first.”
I’ve never spoken to any of the Justices about whether there is such a norm. It appears to me that the debut opinions for six of the current Members of the Court were unanimous (as are many of the Court’s opinions, just under 33% last Term), but the Court’s practice has not been uniform, even during the time of the Rehnquist Court. As noted by Adam Steinman at Concurring Opinions, Justice O’Connor wrote a concurrence to, and Justice Scalia wrote a dissent from, Justice Breyer’s first opinion. See Allied-Bruce Terminix v. Dobson, 513 U.S. 265 (1995). In addition to that, Justice Thomas, joined by Justices O’Connor and Kennedy, dissented from Justice Ginsburg’s first opinion. See John Hancock Mut. Life Ins. Co. v. Harris Trust, 510 U.S. 86 (1993).
If there were any such tradition on the Burger Court, there were definitely exceptions. Justice Marshall (joined by Justices Douglas and Brennan) dissented from then-Justice Rehnquist’s first opinion, see Schneble v. Florida, 405 U.S. 427 (1972), and Justices Douglas and Marshall (joined by Brennan) dissented from Justice Blackmun’s first opinion, see Wyman v. James, 400 U.S. 309 (1971). Both Justice Marshall and Justice Blackmun (joined by Justice White) wrote dissents to what I believe is Justice Powell’s first opinion, see Commissioner v. First Security Bank, 405 U.S. 394 (1972).