Academic journal article Missouri Law Review

It's Probable: Missouri Constitution Article I, Section 15 Requires a Higher Standard to Obtain a Warrant for Real-Time or Prospective CSLI

Academic journal article Missouri Law Review

It's Probable: Missouri Constitution Article I, Section 15 Requires a Higher Standard to Obtain a Warrant for Real-Time or Prospective CSLI

Article excerpt


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.

A. 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. …

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