People retain a reasonable expectation of privacy in their whereabouts and they do not buy a cell phone expecting to be tracked by the government. Warrantless cell phone tracking here violated the state constitution. State v. Earls, 214 N.J. 564, 70 A.3d 630 (2013):
HELD: Article I, Paragraph 7 of the New Jersey Constitution protects an individual’s privacy interest in the location of his or her cell phone. Police must obtain a warrant based on a showing of probable cause, or qualify for an exception to the warrant requirement, to obtain tracking information through the use of a cell phone.
1. A basic cell phone operates like a scanning radio and contacts the nearest site every seven seconds. Cell phones can be tracked so long as they are not turned off. With advances in technology, cell-phone providers today can pinpoint the location of a person’s cell phone with increasing accuracy — to within buildings and even within individual floors and rooms within buildings in some areas.
2. The United States Constitution guarantees “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures ….” U.S. Const. amend. IV. To determine whether a violation of the Fourth Amendment had occurred, earlier cases focused on whether the government had violated an individual’s reasonable expectation of privacy. Two cases that addressed the government’s use of beepers or electronic tracking devices, United States v. Knotts, 460 U.S. 276, 103 S. Ct. 1081, 75 L. Ed. 2d 55 (1983) and United States v. Karo, 468 U.S. 705, 104 S. Ct. 3296, 82 L. Ed. 2d 530 (1984), found no reasonable expectation of privacy in the monitoring of tracking devices in public, as opposed to private, areas. Decisions that have applied Knotts and/or Karo to cell-site data are divided. Some have found no violation of the Fourth Amendment, while others have found that the Fourth Amendment requires that police get a warrant to obtain cell-site data. A more recent decision of the United States Supreme Court rested on principles of trespass. United States v. Jones, 565 U.S. ___, 132 S. Ct. 945, 181 L. Ed. 2d 911 (2012).
3. This Court has found that Article I, Paragraph 7 of the New Jersey Constitution provides greater protection against unreasonable searches and seizures than the Fourth Amendment. When people make disclosures to phone companies and other providers to use their services, they are not promoting the release of personal information to others. Instead, they can reasonably expect that their personal information will remain private. Using a cell phone to determine the location of its owner is akin to using a tracking device and can function as a substitute for 24/7 surveillance without police having to confront the limits of their resources. It also involves a degree of intrusion that a reasonable person would not anticipate. Details about the location of a cell phone can provide an intimate picture of one’s daily life and reveal not just where people go — which doctors, religious services, and stores they visit — but also the people and groups they choose to affiliate with. That information cuts across a broad range of personal ties with family, friends, political groups, health care providers, and others. In addition, modern cell phones blur the historical distinction between public and private areas because phones emit signals from both places.
4. The focus under the State’s search-and-seizure jurisprudence is on reasonable expectation of privacy concerns. As a general rule, the more sophisticated and precise the tracking, the greater the privacy concern. Today, cell phones can be pinpointed with great precision, but courts are not adept at calculating a person’s legitimate expectation of privacy with mathematical certainty. What is clear is that cell phones are not meant to serve as tracking devices to locate their owners wherever they may be. No one buys a cell phone to share detailed information about their whereabouts with the police. Article I, Paragraph 7 of the New Jersey Constitution protects an individual’s privacy interest in the location of his or her cell phone. Police must obtain a warrant based on a showing of probable cause, or qualify for an exception to the warrant requirement, to obtain tracking information through the use of a cell phone.
5. This opinion announces a new rule of law by imposing a warrant requirement. In determining whether today’s holding should be applied retroactively, the Court must consider several factors, including “the effect a retroactive application would have on the administration of justice.” State v. Knight, 145 N.J. 233, 251, 678 A.2d 642 (1996). The results in many cases would be jeopardized if the Court applied its holding in this case retroactively, causing a disruption in the administration of justice. Thus, the Court applies today’s holding to defendant Earls and future cases only. As to future cases, the warrant requirement will take effect thirty days from today to allow the Attorney General adequate time to circulate guidance to all state and local law enforcement officials. For prior cases, the requirement in place at the time an investigation was conducted remains in effect. Starting January 12, 2010, law enforcement officials had to obtain a court order to get cell-site information under N.J.S.A. 2A:156A-29(e).
6. Under the plain view doctrine, the State cannot show that the officers were lawfully in the motel room because their presence flowed directly from a warrantless search of T-Mobile’s records. Because the Appellate Division found that defendant had no privacy interest in his cell-phone location information and that the plain view doctrine applied, the panel did not consider the emergency aid doctrine. The Court remands the matter to the Appellate Division to determine whether the emergency aid doctrine applies to the facts of this case under the newly restated test.
The judgment of the Appellate Division is REVERSED, and the matter is REMANDED to the Appellate Division for further proceedings consistent with the Court’s opinion.

