It's probable: Missouri Constitution article I, Section 15 requires a higher standard to obtain a warrant for real-time or prospective CSLI.

Author:Hadlow, Aaron
Position:Cell site location information

    There are more active cell phones in the United States than there are people. (1) Law enforcement officers often use electronic communication data during criminal investigations to surveil suspects. (2) Law enforcement officers are able to do so because cell phone ownership is nearly universal. (3) Cell phones emit signals to the nearest cell phone tower every seven seconds. (4) Once the signal is received by the cell tower, it is recorded in signal logs, which are stored by cell service providers. (5) This information is called "cell-site location information" ("CSLI"). (6) Under federal statute, law enforcement may access these records as both historic data and as real-time CSLI. (7) Historic CSLI is a record retained by the cell service provider of the cell phone's signal transmissions to cell towers. (8) Real-time CSLI is the data "stream[ed] continuously" by a cell phone to a cell tower. (9) In most cases, an authorized governmental authority can access this information without knowledge of the phone's user. (10)

    The scope of this Note primarily deals with issues surrounding real-time CSLI, although the issues implicated by article I, section 15 of the Missouri Constitution could apply to historic CSLI as well. Part II of this Note discusses general principles of Fourth Amendment law and the Supreme Court's treatment of searches and seizures in relation to electronic communications and data. It then discusses the statutory developments empowering law enforcement to use emerging technologies for surveillance purposes. Part III discusses recent developments in search and seizure law. It then discusses Missouri's recent amendment to its constitution, which provides additional protections for electronic communications and data. Part IV discusses the impact of recent legal developments on CSLI and law enforcement practice.


    Part II is broken into three parts. Part A reviews the general principles of Fourth Amendment law. Part B discusses the Supreme Court's development of surveillance law under the Fourth Amendment. Part C sketches the development of the modern surveillance statutory scheme under which Missouri law enforcement operates.

    1. Fourth Amendment General Principles

      The Fourth Amendment has two clauses. The first clause (the search and seizure clause) reads: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated ...." (11) The second clause (the warrants clause) reads: "and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." (12) A seizure is "some meaningful interference with an individual's possessory interests in that property." (13) A search within the meaning of the Fourth Amendment has never been explicitly defined by the Supreme Court of the United States. (14) However, law enforcement's access of CSLI has for many years been treated as a search. (15) Prior to 1967, the Supreme Court generally held that, in order for a search to occur, within the meaning of the Fourth Amendment, there had to be some physical intrusion into a "constitutionally protected area." (16) Constitutionally protected areas were limited to those enumerated in the text of the Fourth Amendment. (17) This was known as the trespassory doctrine. (18) In 1967, the Supreme Court turned away from this approach in Katz v. United States. (19)

      In Katz, Charles Katz was convicted of transmitting wagering information by telephone across state lines in violation of federal gambling laws. (20) During trial, recordings of Katz's phone conversations were admitted into evidence. (21) The evidence was obtained after FBI agents had attached an "electronic listening and recording device" to the outside of the public telephone booth that Katz used to place the incriminating phone calls. (22) The Supreme Court was called on to determine whether the evidence was obtained in violation of the Fourth Amendment and therefore erroneously admitted into evidence. (23) The Court dismissed the State's argument that the search was permissible under the Fourth Amendment because there was no physical trespass. (24) Instead, the Court ruled that "the Fourth Amendment protects people, not places." (25)

      In Katz, Justice Harlan articulated in a concurrence the two-part test now known as the Katz test: "[F]irst[,] that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as 'reasonable.'" (26) The Katz ruling required law enforcement to obtain a warrant under the probable cause standard in order to conduct similar surveillance activities in the future. (27)

      While Katz was a turning point in Fourth Amendment search doctrine, Supreme Court case law relating to the warrant clause of the Fourth Amendment has followed its own line of development. Given the practical realities of the work of law enforcement, a number of exceptions to the warrant requirement have been carved out over the years. (28) However, courts always prefer that police officers obtain a warrant before a search. (29) Federal Rule of Criminal Procedure 41, which most surveillance statutes refer to for warrant requirements, generally tracks the language of the Fourth Amendment, requiring the warrant to (1) describe the identity of the person or property to be searched or seized, (2) be issued by a magistrate judge or a judge of a state court of record, and (3) be served within a specified time period no longer than fourteen days after issuance. (30)

      If some governmental act is deemed a search within the meaning of the Fourth Amendment, then regardless of whether it falls under an exception to the warrant requirement, it must be supported by probable cause. (31) Probable cause has its own definitional difficulties. (32) Generally, probable cause evaluations use a multi-factor, objective test: "[W]ould the facts available to the officer at the moment of the seizure or the search 'warrant a man of reasonable caution in the belief' that the action taken was appropriate." (33) Determining whether sufficient evidence exists to support probable cause depends on a balancing test, weighing the invasiveness of the privacy interest against the nature of the immediacy at hand. (34)

    2. Historic Surveillance Law Cases

      As demonstrated in Katz, warrant and probable cause requirements in surveillance cases can raise interesting questions when criminals try to outpace law enforcement in the utilization of new technology.

      The next major (35) development in surveillance law came in two beeper cases decided a year apart. (36) In United States v. Knotts, a beeper was hidden in a vat of chloroform that was used to locate a 3M employee who had stolen the chemical for purposes of manufacturing methamphetamine. (37) Law enforcement was able to closely follow the employee and locate the employee by using a monitoring device that captured the beeper's signal. (38) Once the signal was determined stationary at a secluded cabin in rural wisconsin, police surveilled the cabin and secured a search warrant. (39) Law enforcement did not track the movement of the vat inside the cabin. (40) Later, evidence of the warrantless monitoring of the vat was admitted at trial. (41) In applying Katz, the Supreme Court held that that the governmental surveillance at issue amounted to the following of an automobile on public streets and highways, a place where the defendant had no reasonable expectation of privacy in his movements. (42) It further held that the defendant did not have a subjective expectation of privacy. (43) Since the search satisfied both prongs of the Katz test, the Court concluded there was no unreasonable search at issue. (44)

      United States v. Karo presented the Supreme Court with another case involving law enforcement's use of a beeper hidden inside a container of ether. (45) The Court resolved the question left open by Knotts: whether the initial installation of a beeper in a drum of chemicals was a search when the drum was delivered to a buyer who had no knowledge of the hidden beeper. (46) Again applying Katz, the Court found that the recipient of the chemical drum had no subjective or reasonable expectation of privacy at the time of the installation of the beeper because he did not have possession of the drum at the time. (47) Further, whatever reasonable expectation of privacy the recipient had was diminished when he consented to the possibility of something--including a beeper--being inside the drum that was not supposed to be there upon transfer of possession. (48)

      The Supreme Court emphasized that although the installation of the beeper did not constitute a search or seizure under Katz, it was still possible that an illegal search took place if the drum was monitored in a place the recipient did have an actual or reasonable expectation of privacy, such as his residence. (49) The Court further held that monitoring such devices required a warrant but left open the possibility of exceptions under exigent circumstances. (50)

      Knotts and Karo represent the Supreme Court's approach to cases where law enforcement uses digital signals to locate suspects, an approach the Court used for the next quarter century.

    3. Modern Surveillance Statutory Scheme

      Surveillance law in Missouri operates under the federal statutory scheme. (51) CSLI is accessed by law enforcement officers under a federal law, the Stored Communications Act (the "SCA"). (52) The SCA requires companies, after receiving a proper application, to disclose the "contents" or "records" of electronic communications. (53) An "electronic communication" is "any transfer of signs, signals, writing, images, sounds, data, or intelligence... transmitted... by a wire, radio, electromagnetic, photoelectronic[,] or photooptical system." (54) Importantly,...

To continue reading