In addition to his many judicial bona fides, Justice Antonin Scalia was an underappreciated defender of the Fourth Amendment. With his typical thoroughness and deep textualism that reshaped American judging, the late conservative icon threw out convictions of individuals who were arrested as a result of unconstitutional violations. In Kyllo v. United States (2001), police illegally took thermal images of a man’s home to find a marijuana grow operation. In United States v. Jones (2012), a man had his Jeep tracked with GPS devices without a warrant, leading to a drug trafficking conviction. And in Florida v. Jardines (2013), police brought a drug dog onto a man’s porch to indicate drug activity inside, again, a marijuana grow operation. To Justice Scalia, the sanctity of a person’s home and property—beyond the “reasonable expectation of privacy” standard that dominates Fourth Amendment jurisprudence—was to be held above the governmental interests in fighting crime.

In Kyllo, Scalia wrote for a divided 5–4 majority that included Justices Clarence Thomas, Ruth Bader Ginsburg, David Souter, and Stephen Breyer: “The Fourth Amendment’s protection of the home has never been tied to the measurement of the quality or quantity of information obtained….In the home, our cases show, all details are intimate details, because the entire area is held safe from prying government eyes.” In Jardines, another non-traditional 5–4 split in which he was joined by Justices Thomas, Ginsburg, Sonia Sotomayor, and Elena Kagan, Scalia affirmed this dedication to the home, writing “[W]hen it comes to the Fourth Amendment, the home is first among equals.”

Jones was unanimous and, consequently, one of his dryer decisions lacking both colorful barbs and grand statements about the Fourth Amendment itself. However, it bore the Scalian hallmark of deep historical consideration of the government intrusion, and the Court ultimately rejected the warrantless tracking of Mr. Jones’ Jeep.

When unencumbered by a coalition for a majority or unanimous opinion, Scalia famously unleashed his contempt for specious arguments in his dissenting opinions. In Maryland v. King (2013), a case in which the state of Maryland prevailed on warrantless DNA collection from arrestees, Scalia set the tone at the beginning:

“The Fourth Amendment forbids searching a person for evidence of a crime when there is no basis for believing the person is guilty of the crime or is in possession of incriminating evidence. That prohibition is categorical and without exception; it lies at the very heart of the Fourth Amendment.”

Scalia, joined by Justices Ginsburg, Kagan, and Sotomayor, picked apart the majority’s claim that identification was the target of the collection. The idea that a person who had been fingerprinted, had retained counsel, and had filed motions in court, needed to be identified by DNA testing “taxes the credulity of the credulous.” The government, the dissenters claimed, was trying to gather evidence of other crimes not related to the crime for which he had been charged. Scalia added, “Solving unsolved crimes is a noble objective, but it occupies a lower place in the American pantheon of noble objectives than the protection of our people from suspicionless law-enforcement searches. The Fourth Amendment must prevail.”

Scalia wasn’t perfect on the issue. For example, he signed on to the majority opinion in Kentucky v. King (2011), which said police officers who knock on a door without suspicion can enter the residence to stop the destruction of evidence, arguably creating their own ‘exigent circumstances’ exception to the warrant requirement. Only Justice Ginsburg dissented in that case.

But, generally speaking, Justice Scalia understood that the Fourth Amendment should protect all Americans from the insecurity that comes from roving watchers and investigators equipped with ever-evolving technologies and tactics. While it may be tempting to balance law enforcement interests to keep “guilty” people in prison, Scalia recognized the importance of limiting the government’s ability to impose upon the lives and homes of American citizens in criminal investigations.

Unfortunately, concurrences in these cases and other opinions demonstrate that most of the remaining justices are still wed to the utterly arbitrary—and thus inherently unreliable—“reasonable expectation of privacy” standard laid out in Katz v. United States (1967). My colleague Jim Harper calls the Katz standard “a one-way ratchet against privacy and Fourth Amendment protection.” Scalia, on the other hand, used Katz to broaden the traditional common-law trespass rules dating back centuries, not supplant them with judicial determinations of privacy expectations.

Because the Fourth Amendment is neither a hot-button political issue that dominates nomination fights nor is its support easily predictable on the left-right divide, a nominee from either party—most likely a tabula rasa given present political circumstances—is not very likely to be a stalwart guardian of Fourth Amendment rights.

Court watchers and legal scholars will take years to comprehend the sum of Justice Scalia’s profound impact on the Supreme Court and American law. While a celebrated conservative, Scalia’s jurisprudence was not easily pigeonholed and his Fourth Amendment jurisprudence should not be forgotten. As law enforcement will continue to find new ways to get around the Fourth Amendment, we can only hope that the successor to his seat on the bench carries on this important but overlooked part of his legacy. In the meantime, the American public has one fewer protector against unconstitutional police intrusion.

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