Roger Pilon and Jim Harper have already commented on the substance of Maryland v. King, but I wanted to highlight an aspect of the ruling that has raised some eyebrows, the lineup of justices. Justice Kennedy wrote the majority opinion, joined by Chief Justice Roberts and Justices Thomas, Alito, and Breyer. Meanwhile, Justices Ginsburg, Sotomayor, and Kagan joined Justice Scalia’s hard-hitting dissent. Breyer with the “conservatives,” Scalia leading the “liberals”; what’s going on here?

Not that much, actually, in terms of jurisprudential surprises. As Orin Kerr points out, Justice Scalia has been on the defendants’ side in every non-unanimous Fourth Amendment case — King (DNA-swabbing of arrestees), Bailey (detention incident to search), Jardines (dog-sniffing a home), and McNeely (warrantless blood draw of DUI suspect) — while Justice Breyer has been on the prosecutors’ side in each of those cases.

And the current term isn’t an anomaly. In 2009, for example, Scalia joined the majority in overturning the Court’s precedent that had allowed police to search a car upon arresting its driver in the case of Arizona v. Gant (which Scalia mentions in a law-nerd-witty footnote 6 of his King dissent). The same thing happened in another case that year, Melendez-Diaz v. Massachusetts, this time involving the Sixth Amendment’s Confrontation Clause. Indeed, in both of those 2009 cases, Justices Scalia and Thomas joined Justices Stevens, Souter, and Ginsburg (then also the most “liberal” justices).

What happens in such cases is that the most originalist justices, those who like clear bright-line rules rather than mushy standards or balancing tests, join with justices who bend over backward to grant relief to criminal defendants, against those with law-and-order (Alito) or technocratic (Breyer) or establishmentarian (Roberts, Kennedy) tendencies. Granted, Justice Thomas has been less consistent in that sense this term, but that’s the dynamic to consider when looking at seemingly weird splits in criminal procedure cases.