Cellular communication towers in Emeryville, Calif., in 2014. (Justin Sullivan/Getty Images)

Several federal circuits have ruled on whether the Fourth Amendment protects historical cell-site records. Historical cell-site records are the phone company’s records of what cell tower a phone was connected to in the past. The government often uses those records to roughly locate a person’s phone at that time to show the person’s likely location. A federal statute called the Stored Communications Act (SCA) allows the government to access those records with a court order but does not require a search warrant.

So far, the U.S. Court of Appeals for the 5th Circuit and the en banc 11th Circuit have held that government access to those records is not a Fourth Amendment search and that therefore the SCA’s less-than-a-warrant standard is lawful. The en banc 4th Circuit’s case on the same question is still pending.

Enter the 6th Circuit, which on Wednesday agreed with the 5th and 11th circuits that access to historical cell-site records is not a search. Judge Raymond Kethledge’s opinion in United States v. Carpenter draws heavily on the content/non-content distinction:

This case involves an asserted privacy interest in information related to personal communications. As to that kind of information, the federal courts have long recognized a core distinction: although the content of personal communications is private, the information necessary to get those communications from point A to point B is not. For example, in Ex parte Jackson, 96 U.S. 727, 733 (1878), the Court held that postal inspectors needed a search warrant to open letters and packages, but that the “outward form and weight” of those mailings— including, of course, the recipient’s name and physical address—was not constitutionally protected. Id. That was true even though that information could sometimes bring embarrassment: “In a small village, for instance, a young gentleman may not altogether desire that all the loungers around the store which contains the Post-office shall be joking about the fair object of his affections.” Our Letters, N.Y. Times, Dec. 12, 1872, at 4.

In the twentieth century, the telephone call joined the letter as a standard form of communication. The law eventually followed, recognizing that police cannot eavesdrop on a phone call—even a phone call placed from a public phone booth—without a warrant. See Katz, 389 U.S. at 352-55. But again the Supreme Court distinguished between a communication’s content and the information necessary to send it. In Katz, the Court held that “[t]he Government’s activities in electronically listening to and recording the petitioner’s words” was a search under the Fourth Amendment. Id. at 353 (emphasis added). But in Smith, the Court held that the police’s installation of a pen register—a device that tracked the phone numbers a person dialed from his home phone—was not a search because the caller could not reasonably expect those numbers to remain private. “Although [the caller’s] conduct may have been calculated to keep the contents of his conversation private, his conduct was not and could not have been calculated to preserve the privacy of the number he dialed.” Smith, 442 U.S. at 743 (emphasis in original).

Today, the same distinction applies to internet communications. The Fourth Amendment protects the content of the modern-day letter, the email. See United States v. Warshak, 631 F.3d 266, 288 (6th Cir. 2010). But courts have not (yet, at least) extended those protections to the internet analogue to envelope markings, namely the metadata used to route internet communications, like sender and recipient addresses on an email, or IP addresses. See, e.g., United States v. Christie, 624 F.3d 558, 574 (3d Cir. 2010); United States v. Perrine, 518 F.3d 1196, 1204-05 (10th Cir. 2008); United States v. Forrester, 512 F.3d 500, 510 (9th Cir. 2007).

The business records here fall on the unprotected side of this line. Those records say nothing about the content of any calls. Instead the records include routing information, which the wireless providers gathered in the ordinary course of business. Carriers necessarily track their customers’ phones across different cell-site sectors to connect and maintain their customers’ calls. And carriers keep records of these data to find weak spots in their network and to determine whether roaming charges apply, among other purposes. Thus, the cell-site data—like mailing addresses, phone numbers, and IP addresses—are information that facilitate personal communications, rather than part of the content of those communications themselves. The government’s collection of business records containing these data therefore is not a search.

The third-party doctrine of Smith v. Maryland confirms the point:

The defendants of course lack any property interest in cell-site records created and maintained by their wireless carriers. More to the point, when the government obtained those records, it did “not acquire the contents of communications.” Id. at 741. Instead, the defendants’ cellphones signaled the nearest cell towers—thereby giving rise to the data obtained by the government here—solely “as a means of establishing communication.” Id. Moreover, any cellphone user who has seen her phone’s signal strength fluctuate must know that, when she places or receives a call, her phone “exposes” its location to the nearest cell tower and thus to the company that operates the tower. Accord United States v. Davis, 785 F.3d 498, 511 (11th Cir. 2015) (en banc); In re Application for Historical Cell Site Data, 724, F.3d 600, 614 (5th Cir. 2013). And any cellphone user who has paid “roaming” (i.e., out-of-network) charges—or even cellphone users who have not— should know that wireless carriers have “facilities for recording” locational information and that “the phone company does in fact record this information for a variety of legitimate business purposes.” Id. at 743. Thus, for the same reasons that Smith had no expectation of privacy in the numerical information at issue there, the defendants have no such expectation in the locational information here. On this point, Smith is binding precedent.

Kethledge then distinguishes this case from the concurring opinions in United States v. Jones. First, the way the government obtained the records is very different:

This case involves business records obtained from a third party, which can only diminish the defendants’ expectation of privacy in the information those records contain. See United States v. Miller, 425 U.S. 435, 443 (1976); Phibbs, 999 F.2d at 1077-78. Jones, in contrast, lands near the other end of the spectrum: there, government agents secretly attached a GPS device to the underside of Jones’s vehicle and then monitored his movements continuously for four weeks. That sort of government intrusion presents one set of Fourth Amendment questions; government collection of business records presents another. And the question presented here, as shown above, is answered by Smith.

Second, cell-site information is much less precise than the GPS data in Jones:

GPS devices are accurate within about 50 feet, which is accurate enough to show that the target is located within an individual building. Data with that kind of accuracy might tell a story of trips to “the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on[.]” Jones, 132 S. Ct. at 956 (Sotomayor, J., concurring) (internal quotation marks omitted). But here the cell-site data cannot tell that story. Instead, per the undisputed testimony at trial, the data could do no better than locate the defendants’ cellphones within a 120- (or sometimes 60-) degree radial wedge extending between one-half mile and two miles in length. Which is to say the locational data here are accurate within a 3.5 million square-foot to 100 million square-foot area—as much as 12,500 times less accurate than the GPS data in Jones. And cell phone locational data are even less precise in suburban and rural settings. Areas of this scale might encompass bridal stores and Bass Pro Shops, gay bars and straight ones, a Methodist church and the local mosque.

Finally, Kethledge suggests that the court should be reluctant to second-guess the legislative scheme of the SCA. The greater institutional competence of Congress in changing technology, and Congress’s apparent judgment as to reasonableness in the SCA, “favor leaving undisturbed the Congressional judgment here.”