The Fourth Amendment

The right of the people to be secure in their persons, houses, papers, and effects, against UNREASONABLE SEARCHES AND SEIZURES, shall not be violated, 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.


The basic purpose of the Fourth Amendment is to protect the right to privacy and to ensure freedom from arbitrary invasions for any person in the United States. The first clause in the Fourth Amendment provides protection against unreasonable searches and seizures. A search occurs when an expectation of privacy considered reasonable by society is infringed upon by a government agent or employee, while a seizure is constituted by interference with any individual’s possessory interest in property or their person. Much of the Fourth Amendment is based upon reasonableness, which as a legal entity exists when a reasonable, fair, and rational member of society would recognize it in any given situation.

If an unreasonable search or seizure occurs, any evidence obtained from it is not permissible in court— this is known as the Exclusionary Rule. Subsequently, if evidence from an unconstitutional search leads to any other evidence, that evidence is excluded from consideration in court as well, as it is “fruit from the poisonous tree.” 

The second clause of the Fourth Amendment concerns warrants, a tool commonly used by law enforcement to prevent conducting unconstitutional searches. A key basis for the Fourth Amendment was banning general search warrants, which gave law enforcement effective free reign over private areas and effects with no safeguard for reasonableness. Accordingly, in order to obtain a search warrant in compliance with the Fourth Amendment, law enforcement must demonstrate probable cause, supported by an oath or affirmation, and particularly describe the place to be searched and the items to be seized. 

Probable cause is the central requirement for searches to occur, and it is deemed to exist when there is a reasonable basis for believing that a crime may have been committed and evidence of that crime is present in the place to be searched. Or, that there is a reasonable basis to identifyitems being seized as evidence of a crime. 

However, exceptions to the warrant rule do exist. One such exception is the Plain View Doctrine, which allows law enforcement to take possession of contraband that is not described in thesearch warrant, but is in plain view of the agents. Others include Search Incident to a LawfulArrest, the Automobile Exception, border searches, and the existence of exigent circumstances (when law enforcement has probable cause but no time to obtain a warrant). Additionally, if anyparty provides consent to a search, even without a warrant, the search is reasonable. Ultimately, the Fourth Amendment is a protection from invasion by the government, a way to safeguard our basic right to privacy.



San Jose, California

Early morning on August 22nd, 2009, petitioner David J. Riley was pulled over while driving his Lexus near his home in San Diego, California. Officer Charles Dunnigan pulled Riley over for having expired tags, soon discovered Riley was driving with a suspended license, and accordingly decided to impound petitioner’s car. In accordance with the rules and regulations of the San Diego Police Department, an inventory search of the vehicle was conducted upon its impoundment in order to document its contents. During this inventory search, Officer Dunnigan and another officer whom Dunnigan had called to assist in the search discovered two firearms under the car’s hood. Based on this discovery, Officer Dunnigan placed Mr. Riley under arrest for carrying concealed and loaded weapons. Contemporaneous to the arrest, Officer Dunnigan seized petitioner’s cell phone from his person. The phone was a Samsung Instinct M800 smartphone.

At the scene of the arrest, Officer Dunnigan conducted the first of two warrantless searches of Riley’s phone, scrolling through the phone’s contents and noticing that some words, both in the phone’s contact list and in text messages, normally beginning with the letter “K” were preceded by the letter “C.” Officer Dunnigan believed that this “CK” nomenclature referred to the term “Crip Killers,” a slang term for members of a criminal gang known as the Bloods. Also found during the search of Riley’s person were a green bandana in his pocket and a keychain with a small pair of Converse red and green tennis shoes, items associated with membership in the Lincoln Park gang (a subset of the Bloods).

A few hours later at the police station, Detective Duane Malinowski, a detective specializing in gang investigations, conducted an unsuccessful interrogation with the petitioner, following which Detective Malinowski carried out the second warrantless search of Mr. Riley’s cell phone. In his search of the phone’s contents Detective Malinowski found several photos and videos, including videos of gang initiations through street boxing in which the petitioner can be heard saying “Get him Blood. Brack and Blood on Lincoln,” and pictures depicting the petitioner and others making gang signs, including the hand sign for “L,” in reference to the Lincoln Park gang. One of the photos the detective found pictured the petitioner with another person posing in front of a red Oldsmobile that the police suspected had been involved in a prior shooting. In this prior shooting, three individuals reportedly fired several shots at a passing car before fleeing in a red Oldsmobile, an incident which the police believed was gang related. After discovering the photo’s on Mr. Riley’s phone indicating he owned a red Oldsmobile and was connected to gang activity, and ballistics testing demonstrating that the firearms seized from petitioner’s car were used in the shooting incident, law enforcement came to believe that petitioner was involved in the incident. Mr. Riley and two associates were ultimately charged with shooting at an occupied vehicle, attempted murder, and assault with a semiautomatic firearm. The State also alleged that petitioner had committed these crimes for the benefit of a criminal gang, an allegation which under California law exposed Mr. Riley to enhanced sentencing. (Petitioner was also separately charged in conjunction with the traffic stop with carrying a concealed firearm in a vehicle, carrying a loaded firearm, and receiving stolen property, but those charges are not being contested here).