On Thursday, during the second-to-last day of hearings before the Senate Judiciary Committee, Sen. Patrick Leahy (D-Vt.) had an interesting exchange over recent privacy cases with the Supreme Court judicial nominee, Judge Brett Kavanaugh.

"I've talked repeatedly in this hearing about how technology will be one of the huge issues with the Fourth Amendment going forward," said Kavanaugh, who serves on the United States Court of Appeals for the District of Columbia Circuit.

Opening their six-minute tête-à-tête, Leahy began by asking the appellate court judge about what Kavanaugh wrote in November 2015 in a case known as Klayman v. Obama. In that case, a well-known conservative activist attorney, Larry Klayman, sued the then-president on June 7, 2013—the day after the Snowden revelations became public. The complaint argued that the National Security Agency's telephone metadata program ("Section 215"), which gathered records of all incoming and outgoing calls for years on end, was unconstitutional.

US District Judge Richard Leon ruled in favor of plaintiff and attorney Larry Klayman in December 2013 and ordered that the NSA's program be immediately halted. But he stayed his order pending the government appeal, which reversed Judge Leon in August 2015.

Klayman asked the appeals court to re-hear the case with all of the District of Columbia appellate judges, in what’s known as an en banc appeal. This was denied, and Kavanaugh separately agreed with that decision in a November 2015 concurrence.

"I do so because, in my view, the Government's metadata collection program is entirely consistent with the Fourth Amendment," Kavanaugh wrote. "Therefore, plaintiffs cannot show a likelihood of success on the merits of their claim, and this Court was right to stay the District Court's injunction against the Government’s program. The Government’s collection of telephony metadata from a third party such as a telecommunications service provider is not considered a search under the Fourth Amendment, at least under the Supreme Court's decision in Smith v. Maryland, 442 U.S. 735 (1979). That precedent remains binding on lower courts in our hierarchical system of absolute vertical stare decisis."

Kavanaugh went further, saying that even if the Section 215 metadata program was a search, it should be considered "reasonable" in the name of national security.

"The Fourth Amendment allows governmental searches and seizures without individualized suspicion when the Government demonstrates a sufficient 'special need'—that is, a need beyond the normal need for law enforcement—that outweighs the intrusion on individual liberty," he wrote. "Examples include drug testing of students, roadblocks to detect drunk drivers, border checkpoints, and security screening at airports."

USA Freedom Act

So Sen. Leahy wanted to know why Kavanaugh went out of his way to say this months after Leahy himself had authored a revision in the law, known as the USA Freedom Act, and when two government watchdogs had called for Section 215 to end. (An outside analysis also found in January 2014 that Section 215 was ineffective.)

"I was trying to articulate what I thought based on precedent at the time, when your information went to a third party and when the government went to a third party, the existing privacy Supreme Court precedent was that your privacy interest was essentially zero," Kavanaugh said Thursday. "The opinion by Chief Justice Roberts this past spring in the Carpenter case is a game changer."

Carpenter v. United States involved a suspect, Timothy Carpenter, who was accused of leading an armed robbery gang that hit Radio Shack and other cell phone stores in Michigan and Ohio in 2010 and 2011. The government was able to warrantlessly obtain 127 days' worth of his CSLI from his mobile provider, which detailed precisely where Carpenter had been during that time. The Supreme Court ultimately ruled earlier this year that, when the government seeks to obtain such a large volume of intimate information, it needs to get a warrant first in most cases.

The impact of Carpenter is starting to be felt in cases around the country.

"Do you think if Carpenter had been decided you would have written the concurrence you did in Klayman?" Leahy asked.

"I don't see how I could have," Kavanaugh said.

"Thank you, I agree with that," the Vermont senator replied.

More than the sum of its parts

Sen. Leahy then moved on to a 2012 Supreme Court case, United States v. Jones, which in retrospect has become one of a string of three major pro-privacy decisions that the high court has made within the last decade.

That case began in federal court in Washington, DC, and moved on to the appellate court on which Kavanaugh now sits, the United States Court of Appeals for the District of Columbia Circuit.

Before the Supreme Court agreed to hear Jones, the government, which lost at the appellate level, asked the DC Circuit to reconsider en banc. It declined to do so, but Kavanaugh wrote a dissent in November 2010 even though he was not on the original panel of three appellate judges.

Kavanaugh and three other Circuit judges wrote that Jones, which involved the warrantless placement of a GPS tracker on a suspected drug dealer's car, was very similar to a 1983 decision known as United States v. Knotts.

In that case, the Supreme Court found that there was no "reasonable expectation of privacy" when traveling on a public road. Therefore, a majority concluded, it was OK for the police to put a short-range FM transmitter on a drug suspect's car as it drove 100 miles from Minnesota to Wisconsin.

"The reasonable expectation of privacy as to a person's movements on the highway is, as concluded in Knotts, zero," Kavanaugh wrote in 2010. "The sum of an infinite number of zero-value parts is also zero."

Quoting from this very line during the Friday hearing, Leahy compared Kavanaugh's analysis to a statement as being closer to "the Chinese government than what we'd get from James Madison, had he known about what we can do."

Then, he brought his question home to the present day: "So, because of Carpenter, do you believe there comes a point at which collection of data about a person becomes so pervasive that a warrant would be required even if one collection of one bit of the data would not?"

Mosaic theory

While he didn't come right out and say it, Leahy seemed to be probing whether Kavanaugh ascribes to what many legal scholars call the "mosaic theory." This is the notion that, while a series of discrete surveillance or near-surveillance actions in and of themselves may be legal, there comes a point when those are aggregated over a long enough period of time that they become an unreasonable search in violation of the Fourth Amendment.

Both men undoubtedly knew that the DC appeals court ultimately ruled in favor of the mosaic theory in August 2010 when it handed an intermediate win to Antoine Jones and his co-defendant, Lawrence Maynard.

Kavanaugh reminded the hearing that, in this same dissent, he pointed out that there was a Fourth Amendment violation in the physical attachment of the GPS on Jones' Jeep Grand Cherokee. (This line of reasoning was what was ultimately seized upon by Justice Antonin Scalia and the conservative wing of the Supreme Court.)

But when Kavanaugh addressed whether or not he agreed with the mosaic theory, he was measured in his answer. Kavanaugh seemed to suggest that he disagreed with his DC appeals court colleagues on this point.

"I think the Supreme Court case law in the Riley case, written by Chief Justice Roberts, and the Carpenter case, written by Chief Justice Roberts—both majority opinions—show his and the court's recognition of the issue that you're describing in that technology," Kavanaugh said.

"It's made things different, and we need to understand those differences for purposes of applying Fourth Amendment law now, and I do think those two decisions are quite important. Someone sitting in this chair 10 years from now—the question of technology on Fourth Amendment, First Amendment, [and] War Powers [are] going to be of central importance. I appreciate your question, but I think the Supreme Court case law is developing in a way consistent with your concern."

"Do you think it's consistent with the fact that there will be areas so pervasive that you will need warrants?" Leahy asked.

"The Supreme Court case law is certainly suggesting as much in the Riley and Carpenter case and the Jones GPS case, which I had written the opinion in."

In short, Kavanaugh, in deferring to the government, seemed to acknowledge that he may be in the minority on this point.

The Senate Judiciary Committee is expected to vote on his nomination on September 17, with a full floor vote set to come at the end of the month. With no substantive objection from the Republican majority, Kavanaugh is all but set to be confirmed, in which case he will replace retired Justice Anthony Kennedy, for whom he clerked.