Wednesday, June 15, 2016

The Fourth Amendment, the Wireless Carriers and the Cell Tower Location Data

This post examines an opinion from the U.S. Court of Appeals for the Sixth Circuit:  U.S. v. Carpenter, 2016 WL 1445183 (2016). The court begins by explaining that in
Fourth Amendment cases the Supreme Court has long recognized a distinction between the content of a communication and the information necessary to convey it. Content, per this distinction, is protected under the Fourth Amendment, but routing information is not. Here, Timothy Carpenter and Timothy Sanders were convicted of nine armed robberies in violation of the Hobbs Act. The government's evidence at trial included business records from the defendants' wireless carriers, showing that each man used his cellphone within a half-mile to two miles of several robberies during the times the robberies occurred. The defendants argue that the government's collection of those records constituted a warrantless search in violation of the Fourth Amendment. 
U.S. v. Carpenter, supra.
The opinion goes on to outline the relevant facts in the case:
In April 2011, police arrested four men suspected of committing a string of armed robberies at Radio Shacks and T–Mobile stores in and around Detroit. One of the men confessed that the group had robbed nine different stores in Michigan and Ohio between December 2010 and March 2011, supported by a shifting ensemble of 15 other men who served as getaway drivers and lookouts. The robber who confessed to the crimes gave the FBI his own cellphone number and the numbers of other participants; the FBI then reviewed his call records to identify still more numbers that he had called around the time of the robberies.
U.S. v. Carpenter, supra.
The Court of Appeals went on to explain that, in May and June of 2011,
the FBI applied for three orders from magistrate judges to obtain `transactional records’ from various wireless carriers for 16 different phone numbers. As part of those applications, the FBI recited that these records included `[a]ll subscriber information, toll records and call detail records including listed and unlisted numbers dialed or otherwise transmitted to and from [the] target telephones from December 1, 2010 to present[,]’ as well as `cell site information for the target telephones at call origination and at call termination for incoming and outgoing calls[.]’

The FBI also stated that these records would `provide evidence that Timothy Sanders, Timothy Carpenter and other known and unknown individuals’ had violated the Hobbs Act, 18 U.S. Code § 1951. The magistrates granted the applications pursuant to the Stored Communications Act, under which the government may require the disclosure of certain telecommunications records when `specific and articulable facts show[ ] that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing criminal investigation.’ 18 U.S. Code § 2703(d).
U.S. v. Carpenter, supra.
The Court went on to describe the charges against Carpenter and Sanders and to summarize what occurred at their trial:
The government later charged Carpenter with six counts, and Sanders with two, of aiding and abetting robbery that affected interstate commerce, in violation of the Hobbs Act, and aiding and abetting the use or carriage of a firearm during a federal crime of violence. See 18 U.S. Code §§ 924(c), 1951(a). Before trial, Carpenter and Sanders moved to suppress the government's cell-site evidence on Fourth Amendment grounds, arguing that the records could be seized only with a warrant supported by probable cause. The district court denied the motion.

At trial, seven accomplices testified that Carpenter organized most of the robberies and often supplied the guns. They also testified that Carpenter and his half-brother Sanders had served as lookouts during the robberies. According to these witnesses, Carpenter typically waited in a stolen car across the street from the targeted store. At his signal, the robbers entered the store, brandished their guns, herded customers and employees to the back, and ordered the employees to fill the robbers' bags with new smartphones. After each robbery, the team met nearby to dispose of the guns and getaway vehicle and to sell the stolen phones.

FBI agent Christopher Hess offered expert testimony regarding the cell-site data provided by Carpenter's and Sanders's wireless carriers, MetroPCS and T–Mobile. Hess explained that cellphones work by establishing a radio connection with nearby cell towers (or `cell sites’); that phones are constantly searching for the strongest signal from those towers; and that individual towers project different signals in each direction or `sector,’ so that a cellphone located on the north side of a cell tower will use a different signal than a cellphone located on the south side of the same tower. Hess said that cell towers are typically spaced widely in rural areas, where a tower's coverage might reach as far as 20 miles. In an urban area like Detroit, however, each cell site covers `typically anywhere from a half-mile to two miles.’ He testified that wireless carriers typically log and store certain call-detail records of their customers' calls, including the date, time, and length of each call; the phone numbers engaged on the call; and the cell sites where the call began and ended.
U.S. v. Carpenter, supra.
The court ended its preface by noting that, with the
cell-site data provided by Carpenter's and Sanders's wireless carriers, Hess created maps showing that Carpenter's and Sanders's phones were within a half-mile to two miles of the location of each of the robberies around the time the robberies happened. Hess used MetroPCS call-detail records, for example, to show that Carpenter was within that proximity of a Detroit Radio Shack that was robbed around 10:35 a.m. on December 13, 2010. Specifically, MetroPCS records showed that at 10:24 a.m. Carpenter's phone received a call that lasted about four minutes.

At the start and end of the call, Carpenter's phone drew its signal from MetroPCS tower 173, sectors 1 and 2, located southwest of the store and whose signals point north-northeast. After the robbery, Carpenter placed an eight-minute call originating at tower 145, sector 3, located northeast of the store, its signal pointing southwest; when the call ended, Carpenter's phone was receiving its signal from tower 164, sector 1, alongside Interstate 94, north of the Radio Shack. See Carpenter App'x at 11. Hess provided similar analysis concerning the locations of Carpenter's and Sanders's phones at the time of a December 18, 2010 robbery in Detroit; a March 4, 2011 robbery in Warren, Ohio; and an April 5, 2011 robbery in Detroit. . . .
U.S. v. Carpenter, supra.
Finally, the opinion notes that the jury
convicted Carpenter and Sanders on all of the Hobbs Act counts and convicted Carpenter on all but one of the § 924(c) gun counts. Carpenter's convictions on the § 924(c) counts subjected him to four mandatory-minimum prison sentences of 25 years, each to be served consecutively, leaving him with a Sentencing Guidelines range of 1,395 to 1,428 months' imprisonment. The district court sentenced Carpenter to 1,395 months' imprisonment and Sanders to 170 months' imprisonment. Carpenter and Sanders now appeal their convictions and sentences.
U.S. v. Carpenter, supra.
The Court of Appeals then took up Carpenter’s and Sanders’
challenge the district court's denial of their motion to their cell-site data from the evidence at trial. Those data themselves took the form of business records created and maintained by the defendants' wireless carriers: when the defendants made or received calls with their cellphones, the phones sent a signal to the nearest cell-tower for the duration of the call; the providers then made records, for billing and other business purposes, showing which towers each defendant's phone had signaled during each call. The government thereafter collected those records, and hence these cell-site data, for a range of dates (127 days of records for Carpenter, 88 days for Sanders) encompassing the robberies at issue here.

The government did so pursuant to a court order issued under the Stored Communications Act, which required the government to show `reasonable grounds’ for believing that the records were `relevant and material to an ongoing investigation.’ 18 U.S. Code § 2703(d). Carpenter and Sanders argue that the Fourth Amendment instead required the government to obtain a search warrant, pursuant to a showing of probable cause, before collecting the data. The district court rejected that argument, holding that the government's collection of cell-site records created and maintained by defendants' wireless carriers was not a search under the Fourth Amendment. We review the district court's decision de novo. See United States v. Lee, 793 F.3d 680, 684 (U.S. Court of Appeals for the 6th Circuit 2015).
U.S. v. Carpenter, supra.
It went on to explain that the Fourth Amendment protects
 `[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures[.]’ U.S. Constitution amendment IV. . . . `[F]or most of our history the Fourth Amendment was understood to embody a particular concern for government trespass upon the areas (‘persons, houses, papers, and effects') it enumerates.’ U.S. v. Jones, 132 S.Ct. 945, 950 (2012). Government trespasses upon those areas normally count as a search. Id. In Katz v. U.S., 389 U.S. 347(1967), however, the Supreme Court moved beyond a property-based understanding of the Fourth Amendment, to protect certain expectations of privacy as well. To fall within these protections, an expectation of privacy must satisfy `a twofold requirement’: first, the person asserting it must `have exhibited an actual (subjective) expectation of privacy’; and second, that expectation must `be one that society is prepared to recognize as “reasonable.”’ Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring). When an expectation of privacy meets both of these requirements, government action that `invade[s]’ the expectation normally counts as a search. Smith v. Maryland, 442 U.S. 735, 740, (1979).
U.S. v. Carpenter, supra.
The Court of Appeals then took up the central issue in the case, noting that it
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. . . .
U.S. v. Carpenter, supra.
The court moved on to modern technology, noting that 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 v. United States, supra.  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. . . . 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 v. Maryland, supra (emphasis in original).
U.S. v. Carpenter, supra.
After noting that “[t]oday, the same distinction applies to internet communications”, the court explained that the 
Fourth Amendment protects the content of the modern-day letter, the email. See U.S. v. Warshak, 631 F.3d 266, 288 (U.S. Court of Appeals for the 6th Circuit 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., U.S. v. Christie, 624 F.3d 558, 574 (U.S. Court of Appeals for the 3rd Circuit 2010); U.S. v. Perrine,518 F.3d 1196, 1204–05 (U.S. Court of Appeals for the 10th Circuit 2008); U.S. v. Forrester, 512 F.3d 500, 510 (U.S. Court of Appeals for the 9th Circuit 2008).

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.
U.S. v. Carpenter, supra.
The opinion goes on to note that the Supreme Court’s decision in Smith v. Maryland
confirms the point. At the outset, the Court observed that Smith could not claim that `his “property”' was invaded’ by the State's actions, which meant he could not claim any property-based protection under the Fourth Amendment. And as to privacy, the Court hewed precisely to the content-focused distinction that we make here. Smith v. Maryland, supra. The Court emphasized (literally) that the State's pen register did `not acquire the contents of communications.' Smith v. Maryland, supra. (emphasis in original). Instead, the Court observed, the phone numbers acquired by the State had been dialed `as a means of establishing communication.’ Smith v. Maryland, supra. Moreover, the Court pointedly refused to adopt anything like a `least-sophisticated phone user’ . . . standard in determining whether phone users know that they convey that information to the phone company: `All telephone users realize that they must ‘convey’ phone numbers to the telephone company, since it is through telephone company switching equipment that their calls are completed.’ Smith v. Maryland, supra. The Court likewise charged “telephone users” with knowledge that . . . `the phone company does in fact record this information for a variety of legitimate business purposes.’ Smith v. Maryland, supra. Thus, the Court held, Smith `voluntarily conveyed numerical information to the telephone company and “exposed” that information to its equipment in the ordinary course of business.’ Smith v. Maryland, supra.  Hence the numerical information was not protected under the Fourth Amendment.
U.S. v. Carpenter, supra.
The court then articulated its holding in this case, explaining that the
same things are true as to the locational information here. 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.’ Smith v. Maryland, supra. 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.’ Smith v. Maryland, supra. 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. . . . 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.’ Smith v. Maryland, supra.  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.
U.S. v. Carpenter, supra.

The Court of Appeals ended the opinion by explaining that “[i]n sum, we hold that the government's collection of business records containing cell-site data was not a search under the Fourth Amendment.” U.S. v. Carpenter, supra.

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