Full opinion text
Affirmed by published opinion. Senior Judge DAVIS wrote the majority opinion, in which Judge THACKER joined. Judge THACKER wrote a separate concurring opinion. Judge MOTZ wrote an opinion dissenting in part and concurring in the judgment. DAVIS, Senior Circuit Judge: Appellants Aaron Graham and Erie Jordan appeal their convictions for several offenses arising from a series of armed robberies. Specifically, Appellants challenge the district court’s admission of testimonial and documentary evidence relating to cell site location information (“CSLI”) recorded by their cell phone service provider. We conclude that the government’s warrantless procurement of the CSLI was an unreasonable search in violation of Appellants’ Fourth Amendment rights. Nevertheless, because the government relied in good faith on court orders issued in accordance with Title II of the Electronic Communications Privacy Act, or the Stored Communications Act (“SCA”), we hold the court’s admission of the challenged evidence must be sustained. Jordan separately challenges restrictions on his own testimony imposed by the district court, the court’s denial of his motion for severance, the exclusion of certain out-of-court statements attributed to Graham, the admission of evidence seized during a search of his residence, and the sufficiency of the evidence supporting several of his convictions. Finding no reversible error in these respects, we affirm the judgment of the district court. I. This prosecution arose from a series of six armed robberies of several business establishments located in Baltimore City and Baltimore County, Maryland. After a nine-day joint trial in the U.S. District Court for the District of Maryland, a jury found Appellants guilty on all counts submitted to it. Aaron Graham was convicted of being a felon in possession of a firearm, Hobbs Act robbery, conspiracy to commit Hobbs Act robbery, and brandishing a firearm in connection with all six robberies. Eric Jordan was convicted of conspiracy, Hobbs Act robbery, and brandishing a firearm in connection with three of the robberies. A. The evidence adduced at trial permitted the jury to find the following facts. The first robbery occurred the evening of January 17, 2011, at a Dollar Tree store in Baltimore County. Graham entered the store, brandished a small black gun, and directed a cashier to open a cash register. The cashier removed cash from the register and gave it to Graham. Graham reached over the counter to grab additional cash before fleeing the store. The second and third robberies occurred five days later. On the evening of January 22, 2011, five individuals, including Graham, arrived at Mondawmin Mall in Baltimore in a dark colored Ford F-150 pickup truck, exited the vehicle, and entered the shopping mall before the truck pulled away. Graham, seen on video surveillance wearing the same clothing worn during the Dollar Tree robbery five days earlier, entered the Milan Gold & Diamonds jewelry store (“Milan Gold”) inside the mall with a second individual. After two other individuals entered the store, leaving a fifth standing outside the door, Graham pointed a gun at a clerk and demanded, “Don’t be smart with me. Just give me everything.” J.A. 1522. The three persons with. Graham picked up the jewelry as the clerk removed it from a display case. Graham demanded a specific watch from a separate display case and, after the clerk gave it to him, he and the others left the mall. Later that evening, Graham, again wearing the same clothes, entered a 7-Eleven store in Baltimore, walked behind the counter, grabbed the clerk, and demanded that he open the cash register. The clerk did not see a gun but saw Graham’s hand inside his jacket and later testified that “it felt like there was some kind of weapon, some kind of material in there.... ” J.A. 1600. Graham emptied two cash registers and then ordered the clerk to go into a back room inside the store. After Graham left, the clerk observed Graham enter the driver’s side of an F150 truck and depart. The clerk recorded video of the truck pulling away and its appearance matched that of the truck used at Mondawmin Mall earlier that evening. The fourth robbery occurred on February 1, 2011, at a Shell gas station in Baltimore County. Graham and a masked individual entered the cashier’s booth, where Graham pushed the clerk to the floor, began punching and kicking him, and then brandished a small gun, placing it near the clerk’s ear. Meanwhile, a third individual stood near the door to the store with a sawed-off shotgun. When a customer attempted to leave, the third robber blocked the exit, forced the customer to the ground, and beat him in the head with the shotgun. After Graham and the second robber removed cash from the booth, the three robbers departed. The fifth and sixth robberies occurred four days later. On February 5, 2011, at approximately 3:29 p.m., Graham entered a Burger King restaurant in Baltimore wearing the same jacket worn during the Dollar Tree, Milan Gold, and 7-Eleven robberies, and carrying a small black gun with a white handle. Graham brandished the weapon and demanded money. The restaurant manager opened several cash registers, which Graham emptied before departing. Graham was seen entering a dark colored F-150 truck on the passenger side before the truck pulled away. About forty five minutes later, Graham entered a McDonald’s restaurant approximately two miles from the Burger King, went behind the counter, and demanded money, brandishing a small black gun with a white handle. After the restaurant manager opened three cash registers, Graham removed cash and stuffed it into his jacket before departing. The manager saw Graham enter the passenger side of a dark pickup truck, which pulled away rapidly. While investigating the Burger King robbery, Officer Joshua Corcoran of the Baltimore Police Department received reports describing the robber, his clothing, and the pickup truck. Shortly thereafter, he heard a radio call regarding the McDonald’s robbery and indicating that the pickup truck was possibly headed toward his location. After leaving the Burger King, Corcoran spotted a pickup truck matching the descriptions he received and observed that a passenger inside the vehicle wore a jacket matching the description of that reportedly worn by the Burger King robber. During Corcoran’s pursuit of the truck, the driver drove it up onto a sidewalk and accelerated. Corcoran continued pursuit just before the truck became trapped between heavy traffic, a construction barrier, and a moving train in front of it, and was forced to stop. Corcoran and another officer conducted a felony car stop, directing orders to Graham and the driver, Jordan. Gbaham and Jordan were non-compliant with some of the officers’ instructions but were eventually secured and arrested. At the scene, employees of Burger King and McDonald’s identified Graham as the robber. A black .25 caliber Taurus pistol with a pearl handle was recovered from under the passenger seat. Nearly $1,100 in cash bundles were recovered from the person of Graham and Jordan, and from an open console inside the truck. B. During the ensuing, post-arrest investigation, Detective Chris Woerner recognized similarities between the restaurant robberies and the Milan Gold and 7-Elev-en robberies. Woerner prepared search warrants for Graham’s and Jordan’s residences and the pickup truck. The probable cause portion of each of the warrant affidavits described what was known at the time about the Milan Gold, 7-Eleven, Burger King, and McDonald’s robberies. The search warrants were issued by a judge of the Circuit Court of Maryland for Baltimore City. While Woerner was seeking the warrant for Graham’s residence, other officers conducted a search of Jordan’s apartment, recovering a sawed-off shotgun, a matching shotgun shell, a .357 caliber Rossi revolver, .357 caliber cartridges, and other items. Woerner executed searches of Graham’s residence and the pickup truck, recovering a gun holster and several rings and watches from the residence, and two cell phones from the truck. After Woer-ner obtained warrants for the phones, the phone numbers associated with each phone was determined and matched the respective numbers disclosed by Graham and Jordan after their arrest. Woerner contacted the Baltimore County Police Department to determine whether they were investigating any potentially related robberies, sending photos of Graham and Jordan and photos from the searches. Detective Kelly Marstellar recognized similarities to the Dollar Tree and Shell station robberies, including the similarity between the jacket worn by Jordan at the time of his arrest and that worn by the masked robber of the Shell station, who had entered the cashier booth. The Baltimore County Police Department prepared and executed a second round of search warrants at Graham’s and Jordan’s residences on February 23, 2011. During the second search of Jordan’s apartment, officers recovered clothing that matched that worn by Graham during the Shell station robbery. The government sought cell phone information from Sprint/Nextel, the service provider for the two phones recovered from the truck. Sprint/Nextel identified Graham’s phone as subscribed to Graham’s wife at their shared Baltimore County address and Jordan’s phone as subscribed to an alias or proxy. The government then sought and obtained two court orders for disclosure of CSLI for calls and text messages transmitted to and from both phones. The government’s initial application for a court order sought CSLI for four time periods: August 10-15, 2010; September 18-20, 2010; January 21-23, 2011; and February 4-5, 2011. A second application followed, seeking information for a much broader timeframe: July 1, 2010 through February 6, 2011. The government used the court order to obtain from Sprint/Nextel records listing CSLI for this 221-day time period. C. The government charged Graham and Jordan with multiple counts of being felons in possession of a firearm, see 18 U.S.C. § 922(g)(1) (2011); robbery affecting commerce, see 18 U.S.C. § 1951(a) (Hobbs Act); conspiracy to commit Hobbs Act robbery, see id.; brandishing a firearm during a crime of violence, see 18 U.S.C. § 924(c); and conspiracy to brandish a firearm during a crime of violence, see 18 U.S.C. § 924(o). Jordan was also charged with possession of an unregistered sawed-off shotgun. See 18 U.S.C. § 5861(d). The indictment also charged aiding and abetting the felon-in-possession, Hobbs Act robbery, conspiracy, and brandishing-a-firearm offenses. See 18 U.S.C. § 2. Graham was charged in connection with all six robberies, and Jordan was charged in connection with the Shell, Burger King, and McDonald’s robberies. Appellants filed a number of pre-trial motions, including motions for severance under Rule 14 of the Federal Rules of Criminal Procedure and a motion to suppress the CSLI obtained from Sprint/Nex-tel on Fourth Amendment grounds. Jordan separately filed a motion to suppress evidence seized during the search of his apartment, arguing that the first search warrant was defective. The district court denied all of Appellants’ motions, and the case proceeded to trial. During trial, Appellants objected to proposed testimony regarding CSLI from a Sprint/Nextel records custodian and from an FBI agent who investigated the case, arguing that the proposed testimony was impermissible expert opinion. The district court disagreed and admitted the proposed testimony. Jordan also filed a motion in limine seeking to admit a handwritten statement purportedly written by Graham and a recorded telephone call in which Graham participated. The court denied the motion, excluded the handwritten statement as hearsay and unauthenticated, and excluded the phone call as irrelevant. The court also ordered that the scope of Jordan’s testimony be limited to exclude certain irrelevant topics that were potentially prejudicial to Graham. At the close of the government’s case, the government moved to dismiss the count of conspiracy to possess a firearm during a crime of violence. Graham and Jordan moved for judgment of acquittal as to all remaining counts for insufficiency of evidence under Rule 29(a) of the Federal Rules of Criminal Procedure. The court denied the defendants’ Rule 29(a) motions, except with respect to the felon-in-possession count, which the court granted as to Jordan. Jordan’s defense case consisted of his own testimony as well as that of four character witnesses and a private investigator. Graham declined to testify and offered no evidence. The parties rested on April 26, 2012, and delivered closing arguments the following day. On April 30, 2012, the jury returned guilty verdicts on all remaining counts. Graham and Jordan submitted motions for new trials, which the district court denied. This appeal followed. D. During the pendency of this appeal, pri- or to oral argument, this Court directed each party to file a supplemental brief addressing the U.S. Supreme Court’s recent decision in Riley v. California, — U.S.-, 134 S.Ct. 2473, 189 L.Ed.2d 430 (2014), and permitted Appellants to file a supplemental reply brief. Dkt. No. 135. Appellants filed their supplemental brief on July 18, 2014, Dkt. No. 138; the government filed its supplemental response brief on August 4, 2014, Dkt. No. 142; and Appellants filed a supplemental reply brief on August 8, 2014, Dkt. No. 144. On August 21, 2014, the government filed a letter with the Court requesting permission to identify what it called “erroneous factual assertions” in Appellants’ supplemental reply and seeking to rebut several assertions made in that brief. Dkt. No. 145. The next day, Appellants filed a motion to strike the government’s letter as a sur-reply, Dkt. No. 146, to which the government did not respond. The government’s submission is, in effect, a sur-reply brief in the form of a letter. This Court does not generally permit the filing of sur-reply briefs without first granting leave for such a filing. Moreover, the government’s letter fails to make an adequate demonstration of the need for a sur-reply. Accordingly, we grant the motion to strike, deny the government’s request, and do not consider the content of the government’s letter in disposition of this appeal. E. Graham and Jordan present several issues on appeal, arguing that the district court erred in admitting the government’s CSLI evidence and certain testimony of the case agent and the Sprint/Nextel records custodian regarding the CSLI. Jordan argues separately that the district court also committed constitutional error in restricting his testimony and erred in denying his severance motion, excluding the out-of-court statements attributed to Graham, and admitting evidence seized from his apartment. Jordan argues further that the evidence presented at trial was insufficient to support convictions for conspiracy, Hobbs Act robbery, or brandishing a firearm during a crime of violence. We consider these issues in turn. II. During the investigation of the robberies charged in this case, the government secured court orders under the SCA for 221 days’ worth of historical CSLI from Sprint/Nextel. Appellants filed a motion to suppress use of the CSLI at trial, arguing that the government’s acquisition of the records without a warrant based on probable cause was an unreasonable search in violation of the Fourth Amendment. The district court denied the motion, holding that the government’s conduct was not an unreasonable search and, even if it was, the good-faith exception to the exclusionary rule justified admission of the CSLI. See generally United States v. Graham, 846 F.Supp.2d 384 (D.Md.2012). The government ultimately used the CSLI at trial to establish Appellants’ locations at various times before and after most of the charged robberies. Appellants now appeal the denial of their motion to suppress. We review a district court’s evidentiary rulings for abuse of discretion, United States v. Rivera, 412 F.3d 562, 566 (4th Cir.2005), but we review de novo any legal conclusions as to whether certain law enforcement conduct infringes Fourth Amendment rights, United States v. Brezo, 308 F.3d 430, 433 (4th Cir.2002). For the reasons explained below, we hold that the government’s procurement of the historical CSLI at issue in this case was an unreasonable search. Notwithstanding that conclusion, we affirm the district court’s denial of the suppression motion because, in obtaining the records, the government acted in good-faith reliance on the SCA and the court orders issued under that statute. A. Historical CSLI identifies cell sites, or “base stations,” to and from which a cell phone has sent or received radio signals, and the particular points in time at which these transmissions occurred, over a given timeframe. Cell sites are placed at various locations throughout a service provider’s coverage area and are often placed on towers with antennae arranged in sectors facing multiple directions to better facili-. tate radio transmissions. A cell phone connects to a service provider’s cellular network through communications with cell sites, occurring whenever a call or text message is sent or received by the phone. The phone will connect to the cell site with which it shares the strongest signal, which is typically the nearest cell site. The connecting cell site can change over the course of a single call as the phone travels through the coverage area. When the phone connects to the network, the service provider automatically captures and retains certain information about the communication, including identification of the specific cell site and sector through which the connection is made. By identifying the nearest cell tower and sector, CSLI can be used to approximate the whereabouts of the cell phone at the particular points in time in which transmissions are made. The cell sites listed can be used to interpolate the path the cell phone, and the person carrying the phone, travelled during a given time period. The precision of this location data depends on the size of the identified cell sites’ geographical coverage ranges. Cell sites in urban areas, which have the greatest density of cell sites, tend to have smaller radii of operability than those in rural areas. The cell sites identified in the CSLI at issue in this case covered areas with a maximum radius of two miles, each divided into three 120-degree sectors. B. The government obtained Appellants’ CSLI through use of court orders issued under the SCA directing Sprint/Nextel to disclose the information. The SCA “pro-vid[es] an avenue for law enforcement entities to compel a provider of electronic communication services to disclose the contents and records of electronic communications.” In re Application of U.S. for an Order Pursuant to 18 U.S.C. Section 2703(d) (In re Application (Fourth Circuit)), 707 F.3d 283, 287 (4th Cir.2013); see also 18 U.S.C. §§ 2701-2711 (2010). The statute outlines procedures a governmental entity must follow to procure information from a service provider, treating subscriber account records differently than the content of electronic communications. United States v. Clenney, 631 F.3d 658, 666 (4th Cir.2011) (citing 18 U.S.C. § 2703). Absent subscriber notice and consent, the government must secure a warrant or a court order for subscription account records. 18 U.S.C. § 2703(c)(1). A warrant from a federal district court for the disclosure of subscriber records must be issued pursuant to the Federal Rules of Criminal Procedure, id. § 2703(c)(1)(A), which, in accordance with the Fourth Amendment, require a finding of probable cause by an impartial magistrate, Fed.R.Crim.P. 41(d); see also Payton v. New York, 445 U.S. 573, 588 n. 26, 100 S.Ct. 1371, 63 L.Ed.2d 639 (1980). Section 2703(d) sets out the requirements for a court order for a service provider to disclose subscriber account records. The government must “offer[] specific and articulable facts showing that there are reasonable grounds to believe that ... the records or other information sought[] are relevant and material to an ongoing criminal investigation.” 18 U.S.C. § 2703(d). “This is essentially a reasonable suspicion standard[,]” In re Application (Fourth Circuit), 707 F.3d at 287, in contrast to the substantially higher probable cause standard for securing a warrant. The statute offers no express direction as to when the government should seek a warrant versus a § 2703(d) order. The government obtained two § 2703(d) court orders for the CSLI at issue in this appeal. The first order directed Sprint/Nextel to disclose CSLI records for four time periods amounting to 14 days, and the second order directed disclosure of records for a much broader 221-day time period that included the previously ordered 14 days. Sprint/Nextel disclosed to the government the total 221 days’ worth of CSLI for each Appellant’s phone. C. Appellants argue that the government violated the Fourth Amendment in seeking and inspecting the CSLI at issue here without a warrant based on probable cause. We agree. The Fourth Amendment protects individuals against unreasonable searches and seizures. Katz v. United States, 389 U.S. 347, 353, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967). A “search” within the meaning of the Fourth Amendment occurs where the government invades a matter in which a person has an expectation of privacy that society is willing to recognize as reasonable. Kyllo v. United States, 533 U.S. 27, 33, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001) (citing Katz, 389 U.S. at 361, 88 S.Ct. 507 (Harlan, J., concurring)). A person’s expectation of privacy is considered reasonable by societal standards when derived from “ ‘concepts of real or personal property law or ... understandings that are recognized and permitted by society.’ ” Minnesota v. Carter, 525 U.S. 83, 88, 119 S.Ct. 469, 142 L.Ed.2d 373 (1998) (quoting Rakas v. Illinois, 439 U.S. 128, 143 n. 12, 99 S.Ct. 421, 58 L.Ed.2d 387 (1978)). War-rantless searches are, “as a general matter, ... per se unreasonable under the Fourth Amendment,” although “there are a few specifically established and well-delineated exceptions to that general rule.” United States v. (Earl Whittley) Davis, 690 F.3d 226, 241-42 (4th Cir.2012) (quoting City of Ontario, Cal. v. Quon, 560 U.S. 746, 760, 130 S.Ct. 2619, 177 L.Ed.2d 216 (2010)) (internal quotation marks omitted). We hold that the government conducts a search under the Fourth Amendment when it obtains and inspects a cell phone user’s historical CSLI for an extended period of time. Examination of a person’s historical CSLI can enable the government to trace the movements of the cell phone and its user across public and private spaces and thereby discover the private activities and personal habits of the user. Cell phone users have an objectively reasonable expectation of privacy in this information. Its inspection by the government, therefore, requires a warrant, unless an established exception to the warrant requirement applies. 1. As an initial matter, we are not persuaded that, as the district court stated, SprinVNextel’s privacy policy disproves Appellants’ claim that they had an actual expectation in the privacy of their location and movements. The privacy policy in effect at the time SprinVNextel disclosed CSLI to the government stated as follows: Information we collect when we provide you with Services includes when your wireless device is turned on, how your device is functioning, device signal strength, where it is located, what device you are using, what you have purchased with your device, how you are using it, and what sites you visit. J.A. 957. First, the policy only states that Sprint/Nextel collects information about the phone’s location — not that it discloses this information to the government or anyone else. ■ Second, studies have shown that users of electronic communications services often do not read or understand their providers’ privacy policies. There is no evidence that Appellants here read or understood the Sprint/Nextel policy. 2. The Supreme Court has recognized an individual’s privacy interests in comprehensive accounts of her movements, in her location, and in the location of her personal property in private spaces, particularly when such information is available only through technological means not in use by the general public. a. In United States v. Knotts, 460 U.S. 276, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983), law enforcement officers used a combination of visual surveillance and monitoring of a radio transmitter installed in a container of chloroform to track the container’s movements by automobile to the defendants’ homes. 460 U.S. at 278-79, 103 S.Ct. 1081. In holding that this practice did not infringe upon a reasonable expectation of privacy, the Court emphasized the “limited” nature of the government’s electronic surveillance effort, which was confined to tracking the container’s movement on public roads from its place of purchase to its ultimate destination. Id. at 284, 103 S.Ct. 1081. Although the government tracked the container to a defendant’s private home, there was no indication that the officers continued to monitor the container inside the private space after its public journey had ended. Id. at 285, 103 S.Ct. 1081; see also California v. Ciraolo, 476 U.S. 207, 213, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986) (“The Fourth Amendment protection of the home has never been extended to require law enforcement officers to shield their eyes when passing by a home on public thoroughfares.”). Knotts left unanswered two questions critical to assessing the constitutionality of the government’s conduct in the present case: (1) whether tracking the location of an individual and her property inside a private space constitutes a Fourth Amendment search; and (2) whether locational tracking of an individual and her property continuously over an extended period of time constitutes a search. Courts have answered each of these questions in the affirmative. b. United States v. Karo, 468 U.S. 705, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984), addressed the first question. As in Knotts, government agents surreptitiously used a radio transmitter to track the movements of a chemical container to a private residence, but here the agents continued to monitor the container while it was inside the residence. Karo, 468 U.S. at 709-10, 104 S.Ct. 3296. The Court held that this practice “violate[d] the Fourth Amendment rights of those who have a justifiable interest in the privacy of the residence.” Id. at 714, 104 S.Ct. 3296. The government’s monitoring of the beeper “revealed] a critical fact about the interior of the premises ... that [the government] could not have otherwise obtained without a warrant”: “that a particular article is actually located at a particular time in the private residence and is in the possession of the person or persons whose residence is being watched.” Id. at 715, 104 S.Ct. 3296. “Indiscriminate monitoring of property that has been withdrawn from public view would present far too serious a threat to privacy interests in the home to escape entirely some sort of Fourth Amendment oversight.” Id. at 716, 104 S.Ct. 3296 (footnote omitted). In Kyllo v. United States, 533 U.S. 27, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001), the Court again considered whether the use of technology to discover information hidden in a private home constituted a Fourth Amendment search. The government aimed a thermal imaging device at the petitioner’s home from a public street to detect infrared radiation inside the home, which would allow it to identify the locations and movements of persons and certain objects inside. Id. at 29-30, 121 S.Ct. 2038. The Court held that “[w]here ... the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.” Id. at 40, 121 S.Ct. 2038. Like the searches challenged in Karo and Kyllo, examination of historical CSLI can allow the government to place an individual and her personal property — specifically, her cell phone — at the person’s home and other private locations at specific points in time. “In the home, ... all details are intimate details, because the entire area is held safe from prying government eyes.” Id. at 37, 121 S.Ct. 2038; see also Karo, 468 U.S. at 714, 104 S.Ct. 3296 (“[Pjrivate residences are places in which the individual normally expects privacy free of governmental intrusion not authorized by a warrant, and that expectation is plainly one that society is prepared to recognize as justifiable.”). The Karo and Kyllo Courts recognized the location of a person and her property within a home at a particular time as a “critical” private detail protected from the government’s intrusive use of technology. See Kyllo, 533 U.S. at 37, 121 S.Ct. 2038; Karo, 468 U.S. at 715, 104 S.Ct. 3296. Inspection of long-term CSLI invades an even greater privacy interest than the search challenged in Karo because, unlike a cell phone, the tracking device in Karo was not carried on anyone’s person and therefore was not capable of tracking the location of any individual. Additionally, the private location information discovered in this case covered a remarkable 221 days, potentially placing each Appellant at home on several dozen specific occasions, far more than the single instances discovered in Karo and Kyllo. See Kyllo, 533 U.S. at 30, 121 S.Ct. 2038; Karo, 468 U.S. at 709, 714, 104 S.Ct. 3296. c. The Supreme Court considered long-term electronic location surveillance in United States v. Jones, — U.S.-, 132 S.Ct. 945, 181 L.Ed.2d 911 (2012). In that case, the government, acting without a warrant, installed a Global Positioning System (“GPS”) device on a suspect’s vehicle to track the movements of the vehicle over a 28-day period. Jones, 132 S.Ct. at 948. The D.C. Circuit had decided that this practice was a search because (1) a reasonable individual would not expect that the sum of her movements over a month would be observed by a stranger in public, and (2) this information could reveal “an intimate picture” of her life not disclosed by any one of her movements viewed individually. United States v. Maynard, 615 F.3d 544, 561-64 (D.C.Cir. 2010), aff'd sub. nom. Jones, — U.S. -, 132 S.Ct. 945, 181 L.Ed.2d 911. The Supreme Court unanimously affirmed the D.C. Circuit without reaching full agreement as to the basis for this decision. See Jones, 132 S.Ct. at 954; id. at 964 (Alito, J., concurring in the judgment). The entire Court did agree however that Knotts had explicitly left unanswered the constitutionality of “dragnet type law enforcement practices” like the form of “twenty-four hour surveillance” employed in Jones. Knotts, 460 U.S. at 283-84, 103 S.Ct. 1081; see Jones, 132 S.Ct. at 952 n. 6 (Scalia, J., writing for the majority); id. at 956 n. * (Sotomayor, J., concurring); id. at 963 n. 10 (Alito, J., concurring in the judgment). Justice Sca-lia’s majority opinion, expressing the views of five Justices, held that the government’s installation of the GPS device on the suspect’s vehicle constituted a search under the traditional trespass-based theory of Fourth Amendment protection, bypassing the reasonable-expectation-of-privacy analysis established in Katz. See id. at 949-52. While acknowledging that “[situations involving merely the transmission of electronic signals without trespass would remain subject to Katz analysis,” Justice Scalia declined to address this question. Id. at 953; see also id. at 954 (“It may be that achieving the same result through electronic means, without an accompanying trespass, is an unconstitutional invasion of privacy, but the present case does not require us to answer that question.”). In two concurring opinions, five Justices confronted the Katz question and agreed that “longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy.” Id. at 955 (Soto-mayor, J., concurring); id. at 964 (Alito, J., concurring in the judgment). Justice So-tomayor echoed the D.C. Circuit’s concerns about the government’s ability to record an individual’s movements and aggregate the information “in a manner that enables the Government to ascertain, more or less at will,” private facts about the individual, such as her “political and religious beliefs, sexual habits, and so on.” Id. at 956. Neither concurrence indicated how long location surveillance could occur before triggering Fourth Amendment protection, but, considering the investigation challenged in Jones, Justice AJito stated that “the line was surely crossed before the 4-week mark.” Id. at 964. The privacy interests affected by long-term GPS monitoring, as identified in Maynard and the Jones concurrences, apply with equal or greater force to historical CSLI for an extended time period. See Commonwealth v. Augustine, 467 Mass. 230, 4 N.E.3d 846, 861 (2014) (“CSLI implicates the same nature of privacy concerns as a GPS tracking device.”). “[Citizens of this country largely expect the freedom to move about in relative anonymity without the government keeping an individualized, turn-by-turn itinerary of our comings and goings.” Renée McDonald Hutchins, Tied Up in Knotts? GPS Technology and the Fourth Amendment, 55 UCLA L.Rev. 409, 455 (2007). Much like long-term GPS monitoring, long-term location information disclosed in cell phone records can reveal both a comprehensive view and specific details of the individual's daily life. As the D.C. Circuit stated in Maynard, “A person who knows all of another’s travels can deduce whether he is a weekly church goer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups — and not just one such fact about a person, but all such facts.” 615 F.3d at 561-62; compare Jones, 132 S.Ct. at 955 (Sotomayor, J., concurring) (“GPS monitoring generates a precise, comprehensive record of a person’s public movements that reflects a wealth of detail about her familial, political, professional, religious, and sexual associations.”), with State v. Earls, 214 N.J. 564, 70 A.3d 630, 642 (2013) (“[CSLI] can reveal not just where people go — -which doctors, religious sendees, and stores they visit— but also the people and groups they choose to affiliate with and when they actually do so.”). . Inspection of historical CSLI may provide even more private information about an individual than the locational monitoring challenged in Maynard/Jones. The surveillance at issue in that case was limited to movements of an automobile on public roads. See Jones, 132 S.Ct. at 948. Quite unlike an automobile, a cell phone is a small hand-held device that is often hidden on the person of its user and seldom leaves her presence. As previously discussed, cell phone users regularly carry these devices into their homes and other private spaces to which automobiles have limited access at best. See Augustine, 4 N.E.3d at 861. Thus, unlike GPS monitoring of a vehicle, examination of historical CSLI can permit the government to track a person’s movements between public and private spaces, impacting at once her interests in both the privacy of her movements and the privacy of her home. Considering the multiple privacy interests at stake, it is not surprising that we are not the first court to recognize as objectively reasonable cell phone users’ expectation of privacy in their long-term CSLI. See, e.g., Augustine, 4 N.E.3d at 865-66 (reasonable expectation of privacy in location information shown in historical CSLI records); Earls, 70 A.3d at 632 (reasonable expectation of privacy in location of cell phones); Tracey v. State, 152 So.3d 504, 526 (Fla.2014) (objectively reasonable expectation of privacy in “location as signaled by one’s cell phone”); In re Application of U.S. for an Order Authorizing Disclosure of Location Info, of a Specified Wireless Tel., 849 F.Supp.2d 526, 539 (D.Md.2011) (“reasonable expectation of privacy both in [subject’s] location as revealed by real-time [CSLI] and in his movement where his location is subject to continuous tracking over an extended period of time, here thirty days”); In re Application of U.S. for an Order Authorizing the Release of Historical Cell-Site Info. (In re Application (E.D.N.Y.)), 809 F.Supp.2d 113, 120 (E.D.N.Y.2011) (“reasonable expectation of privacy in long-term cell-site-location records”). Even the Supreme Court, in Riley, specifically cited “[historic location information” as among the heightened privacy concerns presented in government inspection of cell phones, as such information details the user’s “specific movements down to the minute, not only around town but also within a particular building.” 134 S.Ct. at 2490. Taken together, Karo, Kyllo, and the views expressed in Riley and the Jones concurrences support our conclusion that the government invades a reasonable expectation of privacy when it relies upon technology not in general use to discover the movements of an individual over an extended period of time. Cell phone tracking through inspection of CSLI is one such technology. It is possible that the CSLI for a particular cell phone is not very revealing at all because, for instance, the phone has been turned off or it has made few or no connections to the cellular network. But the government cannot know in advance of obtaining this information how revealing it will be or whether it will detail the cell phone user’s movements in private spaces. See Earls, 70 A.3d at 642. We hold, therefore, that the government engages in a Fourth Amendment search when it seeks to examine historical CSLI pertaining to an extended time period like 14 or 221 days. 3. The district court concluded that this case is distinguishable from Karo and Maynard/Jones because the type of locational surveillance at issue in those cases permits real-time tracking with greater precision and continuity than the examination of historical CSLI. See Graham, 846 F.Supp.2d at 391-92, 404. The use of GPS technology challenged in Maynard/Jones permitted law enforcement to track the suspect’s vehicle continuously at every moment “ ’24 hours a day for 28 days[,]’ ” id. at 392 (quoting Maynard, 615 F.3d at 558), while, here, the CSLI records only disclose a finite number of location data points for certain points in time. This distinction is constitutionally insignificant. The Fourth Amendment challenge is directed toward the government’s investigative conduct, i.e., its decision to seek and inspect CSLI records without a warrant. There is no way the government could have known before obtaining the CSLI records how granular the location data in the records would be. If Appellants had been in constant use of their phones as they moved about each waking day — constantly starting and terminating calls — then the government would have obtained a continuous stream of historical location information approaching that of GPS. A similar or greater degree of continuity would have been achieved if Appellants had smartphones that automatically connect to the nearest cell site every few minutes or seconds. As it turns out, the CSLI records did reveal an impressive 29,659 location data points for Graham and 28,410 for Jordan, amounting to well over 100 data points for each Appellant per day on average. This quantum of data is substantial enough to provide a reasonably detailed account of Appellants’ movements during the 221-day time period, including movements to and from the cell-site sectors in which their homes were located. We therefore reject the district court’s suggestion that the CSLI was not sufficiently continuous to raise reasonable privacy concerns. The district court also questioned the precision of the location data itself, concluding that the CSLI did not identify sufficiently precise locations to invade a reasonable privacy expectation. Unlike GPS data, the court found, CSLI “can only reveal the general vicinity in which a cellular phone is used.” Graham, 846 F.Supp.2d at 392. The precision of CSLI in identifying the location of a cell phone depends in part on the size of the coverage area associated with each cell-site sector listed in the records. Service providers have begun to increase network capacity and to fill gaps in network coverage by installing low-power cells such as “microcells” and “femto-cells,” which cover areas as small as 40 feet. The intense competition among cellular networks provides ample reason to anticipate increasing use of small cells and, as a result, CSLI of increasing precision. We must take such developments into account. See Kyllo, 533 U.S. at 36, 121 S.Ct. 2038 (“While the technology used in the present case was relatively crude, the rule we adopt must take account of more sophisticated systems that are already in use or in development.”). In any event, the CSLI at issue here was precise enough, at minimum, to support reasonable inferences about Appellants’ locations at specific points in time. Otherwise, the information would have lacked any probative value at trial. The very reason that the government obtained and introduced the evidence was to establish Appellants’ locations during times surrounding the charged robberies. Investigators and prosecutors must have believed, after analyzing the CSLI, that it was sufficiently precise to establish Appellants’ whereabouts. The fact that inference was required to glean Appellants’ past locations from the CSLI does not ameliorate or lessen in any manner the invasion of privacy. Indeed, the Supreme Court, in Kyllo, specifically rejected “the novel proposition that inference insulates a search.... ” Id. at 36, 121 S.Ct. 2038 (citing Karo, 468 U.S. 705, 104 S.Ct. 3296). We therefore reject the government’s argument that the CSLI was not adequately precise to infringe upon Appellants’ expectations of privacy in their locations and movements. 4. We also disagree with the district court’s and the dissent’s conclusion that Appellants lacked a reasonable expectation of privacy in their CSLI because the CSLI records were kept by Sprint/Nextel in the ordinary course of business. See Graham, 846 F.Supp.2d at 403; post at 380-81. The dissent argues first that “[t]he nature of the governmental activity” at issue in this case sets it apart from Karo, Kyllo, and Jones. Post at 379-80. While Karo, Kyllo, and Jones each involved direct and contemporaneous surveillance by government agents, the locational tracking challenged here was achieved through government inspection of records held by a third party. This distinction is inconsequential. The precedents of this Court and others show that a Fourth Amendment search may certainly be achieved through an inspection of third-party records. See, e.g., Doe v. Broderick, 225 F.3d 440, 450-52 (4th Cir.2000) (holding that detective’s examination of a patient file held by a methadone clinic was a search and, without probable cause, violated the patient’s Fourth Amendment rights); DeMassa v. Nunez, 770 F.2d 1505, 1508 (9th Cir.1985) (holding that “an attorney’s clients have a legitimate expectation of privacy in their client files”); cf. Ferguson v. City of Charleston, 532 U.S. 67, 78, 121 S.Ct. 1281, 149 L.Ed.2d 205 (2001) (holding that patients enjoy a reasonable expectation of privacy that the results of diagnostic tests will not be disclosed to law enforcement without the patient’s consent). That the government acquired Appellants’ private information through an inspection of third-party records cannot dispose of their Fourth Amendment claim. Yet the dissent seizes upon the fact that the government obtained Appellants’ CSLI from a third-party cell service provider and maintains that we have placed our focus on the wrong question. Instead of assessing the reasonableness of Appellants’ expectation of privacy in their “location and movements over time,” our dissenting colleague would frame the question as “whether an individual has a reasonable expectation of privacy in a third party’s records that permit the government to deduce this information.” Post at 380. But even the analyses in the cases upon which the dissent relies focused foremost on whether, under Katz, the privacy expectations asserted for certain information obtained by the government were legitimate. See United States v. Miller, 425 U.S. 435, 442, 96 S.Ct. 1619, 48 L.Ed.2d 71 (1976) (“We must examine the nature of the particular documents sought to be protected in order to determine whether there is a legitimate ‘expectation of privacy’ concerning their contents.” (emphasis added)); Smith v. Maryland, 442 U.S. 735, 742, 99 S.Ct. 2577, 61 L.Ed.2d 220 (1979) (“petitioner’s argument that [the] installation and use [of a pen register] constituted a ‘search’ necessarily rests upon a claim that he had a ‘legitimate expectation of privacy’ regarding the numbers he dialed on his phone.” (emphasis added)). In answering that question, the fact that the information at issue in Miller and Smith was contained in records held by third parties became relevant only insofar as the defendant in each case had “voluntarily conveyed” the information to the third party in the first place. See Miller, 425 U.S. at 442, 96 S.Ct. 1619; Smith, 442 U.S. at 743-44, 99 S.Ct. 2577. It is clear to us, as explained below, that cell phone users do not voluntarily convey their CSLI to their service providers. The third-party doctrine of Miller and Smith is therefore inapplicable here. a. The Supreme Court held in Miller and Smith that “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties.” Smith, 442 U.S. at 743-44, 99 S.Ct. 2577; see also Miller, 425 U.S. at 442, 96 S.Ct. 1619. This is so even if “the information is revealed on the assumption that it will be used only for a limited purpose and the confidence placed in the third party will not be betrayed.” Miller, 425 U.S. at 443, 96 S.Ct. 1619. In Miller, the government used defective subpoenas to obtain financial records from the defendant’s bank. 425 U.S. at 436, 96 S.Ct. 1619. The Court determined first that the defendant could not claim an unconstitutional invasion of his “private papers” because he had neither ownership nor possession of the transactional records at issue. Id. at 440-41, 96 S.Ct. 1619 (citation omitted). Next, the Court turned to the defendant’s claim that the government violated his privacy interests in the contents of the bank records. Id. at 442, 96 S.Ct. 1619. Because such documents “contain only information voluntarily conveyed to the banks and exposed to their employees in the ordinary course of business,” the Court held that the depositor lacks “any legitimate expectation of privacy” in this information. Id. at 442, 96 S.Ct. 1619. “[I]n revealing his affairs to another,” the defendant assumed the risk “that the information [would] be conveyed by that person to the Government.” Id. at 443, 96 S.Ct. 1619. In Smith, a telephone company, at the request of police, utilized a pen register device to record the numbers dialed from the home phone of Michael Lee Smith, a man suspected of robbing a woman and then harassing her through anonymous phone calls. 442 U.S. at 737, 99 S.Ct. 2577. Smith argued that the warrantless installation of the pen register was an unreasonable search. Id. at 737-38, 99 S.Ct. 2577. The Court determined, first, that people generally understand that they must communicate the numbers they dial to the phone company and that the company has facilities for recording and storing this information permanently. Id. at 742, 99 S.Ct. 2577. Even if Smith had an actual expectation of privacy in the numbers he dialed, this would not be a “legitimate” expectation because he “voluntarily conveyed” the numerical information to the phone company and “ ‘exposed’ ” the information to the company’s recording and storage equipment. Id. at 744, 99 S.Ct. 2577. In so doing, Smith “assumed the risk” that the company would disclose this information to law enforcement. Id. We recently applied the third-party doctrine of Miller and Smith in United States v. Bynum, 604 F.3d 161 (4th Cir.2010), where the government served administrative subpoenas on a website operator to obtain a user’s account information. 604 F.3d at 162. Specifically, the government obtained the user’s name, email address, telephone number, and physical address, id. at 164, all information that the user entered on the website when he opened his account, id. at 162. Citing Smith, we determined that, in “voluntarily conveying] all this information” to the Internet company, the user “‘assumed the risk’” that this information would be revealed to law enforcement. Id. at 164 (quoting Smith, 442 U.S. at 744, 99 S.Ct. 2577). The user, therefore, could not show that he had either an actual or an objectively reasonable expectation of privacy in this information. Id. These precedents do not categorically exclude third-party records from Fourth Amendment protection. They simply hold that a person can claim no legitimate expectation of privacy in information she voluntarily conveys to a third party. It is that voluntary conveyance — not the mere fact that the information winds up in the third party’s records — that demonstrates an assumption of risk of disclosure and therefore the lack of any reasonable expectation of privacy. We decline to apply the third-party doctrine in the present case because a cell phone user does not “convey” CSLI to her service provider at all-— voluntarily or otherwise — and therefore does not assume any risk of disclosure to law enforcement. The service provider automatically generates CSLI in response to connections made between the cell phone and the provider’s network, with and -without the user’s active participation. See Augustine, 4 N.E.3d at 862 (“CSLI is purely a function and product of cellular telephone technology, created by the provider’s system network at the time that á cellular telephone call connects to a cell site.”); id. at 863 (describing CSLI as “location-identifying by-product” of cell phone technology). “Unlike the bank records in Miller or the phone numbers dialed in Smith, cell-site data is neither tangible nor visible to a cell phone user.” In re Application of U.S. for Historical Cell Site Data, 747 F.Supp.2d 827, 844 (S.D.Tex.2010), vacated, 724 F.3d 600 (5th Cir.2013). A user is not required to actively submit any location-identifying information when making a call or sending a message. Such information is rather “quietly and automatically calculated by the network, without unusual or overt intervention that might be detected by the target user.” Id. at 833. We cannot impute to a cell phone user the risk that information about her location created by her service provider will be disclosed to law enforcement when she herself has not actively disclosed this information. Notably, the CSLI at issue in this appeal details location information not only for those transmissions in which Appellants actively participated — i.e., messages or calls they made or answered — but also for messages and calls their phones received but they did not answer. When a cell phone receives a call or message and the user does not respond, the phone’s location is identified without any affirmative act by its user at all — much less, “voluntary conveyance.” See In re Application of U.S. for an Order Directing a Provider of Electronic Communication Service to Disclose Records to the Government (In re Application (Third Circuit)), 620 F.3d 304, 317 (3d Cir.2010) (“[W]hen a cell phone user receives a call, he hasn’t voluntarily exposed anything at all.”). We conclude, in agreement with the analysis of the Third Circuit in In re Application (Third Circuit) and that of several state supreme courts, that the third-party doctrine of Smith and Miller does not apply to CSLI generated by cell phone service providers. See id.; Augustine, 4 N.E.3d at 862-63; Tracey, 152 So.3d at 525; see also Earls, 214 N.J. 564, 70 A.3d at 641-42 (categorically rejecting third-party doctrine). b. The Fifth Circuit, in In re Application of U.S. for Historical Cell Site Data (In re Application (Fifth Circuit)), 724 F.3d 600 (5th Cir.2013), and the en banc Eleventh Circuit in United States v. (Quartavious) Davis, 785 F.3d 498 (11th Cir.2015), have reached the opposite conclusion. While acknowledging that the cell phone user “does not directly inform his service provider of the location of the nearest cell phone tower[,]” the Fifth Circuit decided that users voluntarily convey CSLI to their service providers through general use of their cell phones. In re Application (Fifth Circuit), 724 F.3d at 614. In reaching this conclusion, the court relied on the proposition, advanced by the government, that “users know that they convey information about their location to their service providers when they make a call.” Id. at 612. The Eleventh Circuit followed suit, suggesting that because users are generally aware that their calls are connected through cell towers, their use of their phones amounts to voluntary conveyance of “their general location within that cell tower’s range[.]” (Quartavious) Davis, 785 F.3d at 511. We cannot accept the proposition that cell phone users volunteer to convey their location information simply by choosing to activate and use their cell phones and to carry the devices on their person. Cell phone use is not only ubiquitous in our society today but, at least for an increasing portion of our society, it has become essential to full cultural and economic participation. See Quon, 560 U.S. at 760, 130 S.Ct. 2619 (“Cell phone and text message communications are so pervasive that some persons may consider them to be essential means or necessary instruments for self-expression, even self-identification.”); Riley, 134 S.Ct. at 2484 (“[Mjodern cell phones ... are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.”). People cannot be deemed to have volunteered to forfeit expectations of privacy by simply seeking active participation in society through use of their cell phones. “The fiction that the vast majority of the American population consents to warrant-less government access to the records of a significant share of their movements by ‘choosing’ to carry a cell phone must be rejected.” In re Application (E.D.N.Y.), 809 F.Supp.2d at 127, quoted in Tracey, 152 So.3d at 523. Users’ understanding of how cellular networks generally function is beside the point. The more pertinent question is whether users are generally aware of what specific cell sites are utilized when their phones connect to a cellular network. After all, it is the specificity with which CSLI identifies cell sites that allows users’ location to be tracked and raises privacy concerns. We have no reason to suppose that users generally know what cell sites transmit their communications or where those cell sites are located. A cell phone user cannot be said to “voluntarily convey” to her service provider information that she never held but was instead generated by the service provider itself without the user’s involvement. Both the Fifth and Eleventh Circuits emphasized that service providers maintain CSLI records for their own business purposes rather than for law enforcement purposes and on this basis concluded that a subscriber can have no legitimate privacy expectation in the information these records contain. See In re Application (Fifth Circuit), 724 F.3d at 611-12; (Quartavious) Davis, 785 F.3d at 511-12. CSLI records are, however, wholly unlike business records such as “credit card statements, bank statements, hotel bills, purchase orders, and billing invoices,” which the government “routinely” obtains from third-party businesses by subpoena. Id. at 506. These sorts of business records merely capture voluntary commercial transactions to which the business and its individual client or customer are parties. See Miller, 425 U.S. at 442, 96 S.Ct. 1619. CSLI, on the other hand, records transmissions of radio signals in which the cell phone service subscriber may or may not be an active and voluntary participant. We agree with our sister circuits that a service provider’s business interest in maintaining CSLI records is a relevant consideration in determining whether a subscriber can have a legitimate expectation of privacy in this information. But it is not the only consideration. Courts consider not only such “concepts of real or personal property law” in making this determination but also “ ‘understandings that are recognized and permitted by society.’ ” Carter, 525 U.S. at 88, 119 S.Ct. 469 (citation omitted). As we have explained, society recognizes an individual’s privacy interest in her movements over an extended time period as well as her movements in private spaces. The fact that a provider captures this information in its account records, without the subscriber’s involvement, does not extinguish the subscriber’s reasonable expectation of privacy. Applying the third-party doctrine in this context would simply permit the government to convert an individual’s cell phone into a tracking device by examining the massive bank of location information retained by her service provider, and to do so without probable cause. See David Gray & Danielle Citron, The Right to Quantitative Privacy, 98 Minn. L.Rev. 62, 140 (2013) (“If the government lacks legal authority to install and monitor a GPS-enabled tracking device, then it can get the same information by securing locational data from OnStar, Lojac, a cellular phone provider, or any number of ‘apps’ that gather and use locational information as part of their services.” (emphasis added)). This is not a case like Moffo, where a person assumes the risk that an associate or confidante will disclose her communications to law enforcement, see 385 U.S. at 302-03, 87 S.Ct. 408; nor is this a case like Miller, where a person assumes the risk that a bank will disclose her financial transactions to the government, see 425 U.S. at 443, 96 S.Ct. 1619. Cell phone users do not actively or knowingly communicate or “trade” their location information to their service providers as part of the consideration for the services provided, to say nothing of the documentation of such information in reproducible formats. That this information winds up in the provider’s hands as a consequence of how cellular networks function does not and should not affect cell phone users’ reasonable expectations of privacy in this information or society’s respect for that expectation. c. Courts have recognized that not all private information entrusted to third-party providers of communications services is subject to warrantless government inspection. As far back as 1877, the Supreme Court recognized Fourth Amendment protection against warrantless inspection of the contents of mail entrusted to the postal service for delivery. Ex parte Jackson, 96 U.S. 727, 733, 6 Otto 727, 24 L.Ed. 877 (1877). In so holding, the Court recognized a distinction between, on one hand, protected matter “intended to be kept free from inspection, such as letters! ] and sealed packages[,]” and, on the other hand, unprotected matter “purposefully left in a condition to be examined” as well as the “outward form and weight” of sealed articles. Id. The Court continued to recognize this distinction 90 years later in Katz: “What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection .... But what he seeks t