After hearing about today’s 5-4 decision in Maryland v. King, holding (as Jonathan notes below) that the government can collect and analyze DNA incident to arrest without a warrant, some might be surprised that conservative Justice Scalia voted for the defense side while the liberal Justice Breyer voted for the government. They shouldn’t be. In Fourth Amendment cases this Term, that has been a consistent pattern.

Justice Scalia has been on the defense side of every non-unanimous Fourth Amendment case this term: King (today’s case in which he wrote the dissent), Bailey (in which he joined the 6-3 majority), Jardines (in which he wrote the majority), and McNeely (in which he joined the Sotomayor plurality/majority opinion). In contrast, Justice Breyer has been on the government’s side in each of the Term’s non-unanimous Fourth Amendment cases: King (in which he joined Kennedy’s majority), Bailey (in which he wrote the dissent), Jardines (in which he joined the dissent) and McNeely (in which he joined the more government-friendly Roberts concurrence/dissent with Alito).

Some Fourth Amendment cases have drawn out those dynamics in the past. For example, Justice Scalia voted for the defense and Justice Breyer for the government in Arizona v. Gant (2009). But I don’t recall such a consistent run of Fourth Amendment cases in which Justice Scalia was on the defense side and Breyer was on the government side.

What explains the trend? It might just be a coincidence. But I suspect some of it reflects the fact that a lot of the recent cases have involved Fourth Amendment balancing. Scalia dislikes balancing, while Breyer revels in it. Those different instincts may pull their votes in different directions. Also, defense counsel have realized that Justice Scalia is in play in Fourth Amendment cases if you can find him the kind of argument that he finds appealing. So we’re seeing more defense-side briefs targeting Scalia’s vote. But the problem is that Scalia and Breyer look at Fourth Amendment cases in exactly opposite ways. The kind of argument that appeals to Scalia can lose Breyer, and the kind of argument that appeals to Breyer can lose Scalia.