The oral arguments last week on same-sex marriage showed clearly the Supreme Court’s familiar fault line between liberal justices nominated by Democratic presidents and conservatives named by Republicans.

But a decision that got a little lost in the shuffle displayed a different kind of split on the court. And it may become more noticeable as the term continues and the justices dig deep on a part of the Constitution that has divided and vexed their predecessors as well.

The question is how to balance law enforcement interests against the right that the Fourth Amendment gives citizens to be “secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.”

In last week’s takedown of a legendary drug-sniffing police dog named Franky, it was an unlikely sounding coalition of conservatives and liberals unwilling to defer to law enforcement.

Conservative Justices Antonin Scalia and Clarence Thomas joined with the court’s liberal women — Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan — to say that it constituted a “search” under the Fourth Amendment for two police officers to accompany Franky to Joelis Jardines’s front door in Miami. They had received an anonymous tip that Jardines had turned his abode into a full-time “grow house” for marijuana.

The Supreme Court ruled Tuesday that police cannot have drug-sniffing dogs look for evidence without first getting a search warrant. (Alan Diaz/AP)

The cops used Franky’s “alert” at the door as probable cause for getting a search warrant.

The decision delivered last Tuesday was one of the court’s most readable of the term: Dogs seem to bring out the wit in Supreme Court justices.

Scalia quoted an ancient legal doctrine that “holds the property of every man so sacred, that no man can set his foot upon his neighbour’s close without his leave.”

In Miami, Scalia said, “it is undisputed that the detectives had all four of their feet and all four of their companion’s firmly planted on the constitutional protected extension of Jardines’ home.”

There is an implicit license for a visitor to come to someone’s front door, Scalia said, and “it is generally managed without incident by the nation’s Girl Scouts and trick-or-treaters.”

But while it might be routine to find a visitor knocking at the door, Scalia wrote, “to spot that same visitor exploring the front path with a metal detector, or marching his bloodhound into the garden before saying hello and asking permission, would inspire most of us to — well, call the police.”

Kagan wrote separately to say she thought it was an easy decision for courts to throw out the evidence against Jardines, and would base her decision “on privacy as well as property grounds.”

The court’s fourth liberal, Justice Stephen G. Breyer, was on the other side. He and conservatives Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. have been more willing to defer to law enforcement.

Alito wrote the dissent to the case, saying the majority’s decision was “based on a putative rule of trespass law that is nowhere to be found in the annals of Anglo-American jurisprudence.”

He said police have always had the right to go to a person’s front door, and it was no different in this context simply because the officer was accompanied by a dog on a leash. Alito accused Scalia of hyping the whole event: all told, he said, it only took a minute or two.

(The two also presented an amusing lesson on how to present your argument: Scalia never referred to the police dog by name, and said the animal was restrained by a six-foot leash because of his “wild” nature. Alito called out Franky 11 times, and directed the reader to to note that a six-foot leash is “standard equipment.”)

The case is just one of several the court accepted this term that raise Fourth Amendment issues. Earlier, the justices ruled 6 to 3 that people who have left the scene where officers are enforcing a search warrant cannot be stopped and detained without probable cause.

The court has heard oral arguments but has not yet rendered a decision in a case in which police want to be able to draw blood samples from suspected drunken drivers without their consent or a warrant.

And, in what Alito called “perhaps the most important criminal procedure case that this court has heard in decades,” the court heard a challenge to Maryland’s law that allows law enforcement to take DNA samples from those arrested for serious crimes.

That case has not been decided.

Washington lawyer Kannon K. Shanmugam, who represented the Maryland man whose DNA tied him to a different crime from the one for which he was arrested, said the court “seems to be looking for bright-line rules in determining whether police conduct” constituted a “search” for Fourth Amendment purposes.

“And the common thread of the recent decisions is that the court isn’t willing to say that police conduct is constitutional just because the government says it’s effective as a law enforcement tactic,” Shanmugam said.

In the oral arguments in Maryland v. King, the liberal ranks seemed split, with Breyer asking questions sympathetic of Maryland’s law, and Kagan extremely critical.

It was the same on the conservative side. Alito stayed true to his image as perhaps the biggest supporter of government in Fourth Amendment cases.

Scalia’s questions were more disapproving. He often cites criminal procedure cases when he tells audiences that the court is not as predictable as it is sometimes depicted, and that liberal and conservative are not always adequate in describing the justices.

As he said during a speech last fall in Wyoming: “I ought to be the pinup of the criminal defense bar.”

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