“Hailstorm” decision could create turbulence for tracking tactics

By John Grimm
Guest contributor

Last month, the Court of Special Appeals handed down a major Fourth Amendment decision, holding that police need a warrant to use “cell site simulators” to track people’s locations through their mobile phones. State v. Andrews, No. 1496, Md. Ct. Spec. App. (March 30, 2016), involved the warrant-less use of the portable tracking device — also called an “IMSI catcher” and better known by various brand names including “StingRay” or “Hailstorm” — which mimics cellular network towers and causes all cell phones in its range to send a signal with the phone’s unique “international mobile subscriber identity,” or “IMSI,” number. With that number, police can measure the direction and relative strength of the phone’s signal to determine the phone’s location in real time. Because “people have a reasonable expectation that their cell phones will not be used as real-time tracking devices by law enforcement” and “an objectively reasonable expectation of privacy in real-time cell phone location information,” Slip Op. at 2, the court found that use of cell site simulators to track phones is a Fourth Amendment search, and “the government may not use a cell phone simulator without a warrant or, alternatively, a specialized order that requires a particularized showing of probable cause, based on sufficient information about the technology involved to allow a court to contour reasonable limitations on the scope and manner of the search, and that provides adequate protections in case any third-party cell phone information might be unintentionally intercepted,” id. at 64.

In Andrews, the Baltimore City Police Department was searching for Kerron Andrews, a suspect in an attempted murder. They received a “pen register/trap and trace” order — which can be obtained on less than probable cause — from the circuit court, allowing them to monitor the numbers dialed to or from Andrews’ phone. Using this order, police requested call records from Andrews’ wireless carrier.

They also, however, used a Hailstorm cell site simulator to locate Andrews inside a friend’s house, where they arrested him pursuant to a valid arrest warrant. (Police also requested his real-time GPS location from his cellular-service provider, but Andrews did not move to suppress this information and the Court of Special Appeals did not decide whether police needed a warrant to obtain it.) After the arrest, they received a search warrant and found a gun where Andrews had been sitting. Andrews moved to suppress the gun, arguing that it was the fruit of the illegal warrant-less use of the Hailstorm. The circuit court agreed, and the State appealed.

At the Court of Special Appeals, the State argued that, under the “third party” doctrine, Andrews voluntarily provided data to the Hailstorm by using his phone. Some courts have allowed police to recover cell site location information without a warrant on the theory that suspects voluntarily provide it to third parties through the ordinary operation of their phones. But the Court of Special Appeals agreed with the Fourth Circuit’s recent reasoning that “the fiction that the vast majority of the American population consents to warrantless government access to . . . their movements by ‘choosing’ to carry a cell phone must be rejected.” Id. at 47 (quoting United States v. Graham, 796 F.3d 332, 355-56 (4th Cir. 2015), reh’g en banc granted, 624 F. App’x 75 (4th Cir. 2015)). The court also noted that Andrews did not voluntarily send data to the Hailstorm because his phone was responding to the device.

The court also rejected the State’s argument that its pen register/trap and trace order authorized use of the Hailstorm. On its face, the statute permitting these orders is limited to signaling information, and does not apply to location information. And the state law is nearly identical to its federal counterpart, which is limited (by the Communications Assistance for Law Enforcement Act) to non-location information. The order also wasn’t the functional equivalent of a search warrant because it lacked the necessary particularity. Finally, the police could not rely on the good-faith exception to the warrant requirement because the warrant used to search the house was itself the product of an illegal search (use of the Hailstorm) and could not be relied on in good faith.

Andrews is significant for its controversial implications. Indeed, just a few weeks before the Court of Special Appeals decided Andrews, a federal judge in the Eastern District of Wisconsin held that cell phone location tracking is not a Fourth Amendment search, because of the third-party doctrine and because people do not have a reasonable expectation that the government will not track their location through their phones. See United States v. Wheeler, No. 15-cr-216-pp, W.D. Wisc. (March 14, 2016). Moreover, although the Court of Special Appeals did not decide whether other forms of real-time location tracking require a warrant, its holding that people have a reasonable expectation of privacy in their real-time cell phone location does not appear limited to any specific type of technology.

Another key question Andrews leaves primed but unanswered is whether police need a warrant to access historical cell phone location data. Panels on the Fourth and Eleventh Circuits have found reasonable expectations of privacy do exist in historical location data, but the Eleventh Circuit decision was reversed en banc and the Fourth Circuit decision is pending rehearing en banc. United States v. Davis, 754 F.3d 1205 (11th Cir. 2015), rev’d in part en banc, 785 F.3d 498 (11th Cir. 2015); United States v. Graham, 796 F.3d 332, 355-56 (4th Cir. 2015), reh’g en banc granted, 624 F. App’x 75 (4th Cir. 2015). (To add one further wrinkle, the Davis opinion was written by Judge Sentelle, a D.C. Circuit judge sitting by designation in the Eleventh Circuit.) By quoting favorably from the Fourth Circuit’s Graham, the Court of Special Appeals implicitly suggested that Andrews could also extend to historic information. The court also briefly discussed a new Maryland statute — Md. Code Ann. Crim. P. § 1-203.1 — that provides for a court order authorizing real-time location tracking, but declined to decide whether a Section 1-203.1 order satisfies the warrant requirement.[1]

To some degree, Andrews calls into question many popular techniques law enforcement can use, other than a search warrant, to locate suspects through their phones. Perhaps the most immediate question following the court’s decision is whether the State will seek certiorari. Given the public-policy significance of the issues and the division among courts across the country in resolving them, the case seems like a particularly strong candidate for review by the Court of Appeals. Whichever court has the final word, it is almost certain that Andrews will only be the beginning of a line of cases requiring courts to explore the nuances of cell-phone tracking.


[1] The decision appeared to accept that such an order could be valid provided that it is based on probable cause, but also emphasized that an authorizing court must have sufficient information about how the tracking technology operates. It appears that one reason the police asked for a pen register/trap and trace order instead of a warrant is that the Baltimore State’s Attorney’s Office had signed a non-disclosure agreement with Hailstorm’s manufacturer, Harris Corporation, preventing police from describing in any legal proceeding how the Hailstorm works. (The agreement even contemplated that the State would dismiss charges instead of providing information about Harris’s technology.) The Court of Special Appeals rebuked this agreement as “inimical to the constitutional principles we revere,” Slip Op. at 25, and noted that courts cannot perform their constitutional responsibility to determine whether searches are reasonable if they don’t know how the search actually functions.


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