1. The University of Adelaide, School of Computer Science
Criminal Justice Procedure
8th Edition
The University of Adelaide, School of Computer Science
25 February 2019
Chapter 2
The 4th Amendment
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Chapter 2 — Instructions: Language of the Computer

2. The University of Adelaide, School of Computer Science
25 February 2019
Introduction
Chapter 2
The 4th Amendment contains several important concepts to the study of criminal procedure.
Citizens have an expectation of privacy against unwarranted government intrusion into their lives.
The 4th Amendment further contains a warrant requirement.
The warrant must be based on probable cause and must be signed in advance by a neutral and detached magistrate.
The people and items that are the subject of the warrant must be expressly identified and described before officers invade the personal privacy of citizens.
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Chapter 2 — Instructions: Language of the Computer

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Katz v. United States
Chapter 2
Katz was convicted of transmitting wagering information by telephone in violation of the federal statute.
The FBI agents who investigated the case attached an electronic listening and recording device to the outside of the public telephone booth so they could record the conversation
The Fourth Amendment protects people, not places.
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 to preserve as private, even in an area accessible to the public, may be constitutionally protected.
Even though the search in this case was conducted reasonably, the officers did not get a warrant.
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Warrant Requirement
Chapter 2
The Fourth Amendment contains the warrant provision which provides a layer of protection between citizens and government prior to any search or seizure being conducted.
A warrant “refers to a writ from a judge, permitting law enforcement personnel to take some action, such as make an arrest, search a location, or seize some piece of property.”
The first requirement of a valid warrant application involves the articulation of probable cause.
The warrant requirement contains the additional burden of specificity.
Officers seeking a warrant must describe, with particularity, the person or thing to be searched, and the person or thing to be seized.
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Arrests and Searches
Chapter 2
The laws of arrest are covered by the 4th Amendment.
Arrests fall into two categories, those made with arrest warrants, and those made without arrest warrants.
While many arrests are made under the authority of warrants, the majority are warrantless arrests.
Like arrests, searches must be conducted with a warrant, or upon probable cause.
Exceptions to the search warrant requirement include search incident to a lawful arrest, plain view searches, open fields, vehicle exceptions, border and airport searches, and other exigent circumstances.
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Exclusionary Rule
The penalty for improperly conducting a search or seizure is that the evidence obtained will be excluded from the trial through a legal construct known as the exclusionary rule.
Through the early and mid-1900s the exclusionary rule barred illegally seized evidence from federal trials.
In 1961 the exclusionary rule was applied to the states.
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Mapp v. Ohio
Mapp is significant because it applied the same standard of exclusion to unlawfully obtained evidence in state courts that applied in federal courts.
Thus, fourth amendment protections were incorporated to citizens against state invasions of privacy.
Mapp changed the practices of local and state law enforcement to provide 4th Amendment protections, through providing exclusion of evidence as a sanction for conducting illegal searches and seizures.
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United States v. Leon
This case, together with Massachusetts v. Sheppard, which was decided on the same day, are arguably the most important cases decided on the exclusionary rule since Mapp v. Ohio.
In Leon, the issue was the use of a questionable informant and stale information (failing to constitute probable cause), which the judge mistakenly approved.
The Court determined that to exclude the evidence would not serve the purpose of the rule which was designed to deter police misconduct.
Although the underlying warrant was found to be deficient after the fact, the officers had relied on the warrant to conduct what they believed to be a valid search.
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9. Wong Sun v. United States
This case addresses the “tainted fruit of the poisonous tree” aspect of the exclusionary rule.
The exclusionary rules says that any other evidence obtained directly or indirectly as a result of the illegal behavior is not admissible either.
The subsequent evidence is tainted by the original illegality.
This case goes one step further, however, and carves out an exception to the exclusionary rule.
That exception is that the original taint can be overcome by the independent actions of a defendant that purge the initial taint.
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Similar Cases
Another instance in which evidence can be admitted that would otherwise be excluded is that of discovery by an independent source.
Murray v. U.S.- The Supreme Court determined that the government should not be placed in a worse position that it would otherwise be in as long as the evidence was genuinely gather independent of the earlier unlawful police conduct.
The inevitable discovery doctrine states that if the evidence would have been discovered anyway, even without the illegal action on the part of law enforcement, it may be admitted at trial.
Nix v. Williams- The Court stated “exclusion of evidence what would inevitably have been discovered would … put the government in a worse position, because the police would have obtained that evidence if no misconduct had taken place.”
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USA Patriot Act
After the terrorist attacks of September 11, 2001, several pieces of federal legislation were passed with the intent of facilitating the ferreting out of potential future terrorist acts against the United States.
The USA Patriot Act allows the government to:
access stored “wire and electronic communication” like voice mail and .
have enhanced wiretap and electronic surveillance.
perform sneak-and-peak searches.
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Conclusion
At its very core, the Fourth Amendment sets forth limitations of government actions involving citizens.
The Fourth Amendment provides for a warrant requirement that must be followed before searches and seizures meet the presumption of reasonableness.
The exclusionary rule and the fruits of the poisonous tree doctrines call for the exclusion of evidence which is unlawfully obtained by law enforcement.
The USA Patriot Act was largely a response to a terrorist attack on the United States and expanded the authority of the government.
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