Horton v. California

Since the California court's interpretation of the "plain view" ruling conflicted with other courts' interpretations, the U.S. Supreme Court decided to hear the case, which began 21 February 1990. While the Court had established the previously mentioned exceptions to the Fourth Amendment's ban on warrantless searches and seizures, it had to sharpen its view on finding and confiscating of conspicuous belongings not inadvertently found and not listed on a search warrant.

The Court had previously ruled that the item must not only be in plain view but also must be obviously incriminating in character. In addition, the Court found that the search warrant must authorize the police to search a specific place and area from where the evidence is conspicuous and the police must discover it inadvertently. However, Justice Stevens, writing for the majority, disputed this last condition, that the discovery must be inadvertent, for two reasons. First, the majority argued that just because the police expect to find more evidence during a search than the warrant specifies should not invalidate the search, providing that the search remained confined to the area and the duration specified in the warrant or constituted a valid exception to the warrant.

Second, the Court reasoned that other requirements of the Fourth Amendment safeguard against the police using specific warrants as general warrants, thus rendering the inadvertence requirement unnecessary. Because the police must always have a warrant specifying the person, the place, and the items, they can only search a limited area for a limited amount of time, as authorized by the warrant. The Court felt that if the police followed these rules, the inadvertence policy did not provide any further protection of Fourth Amendment rights, because once the police strayed outside of the specified area of search, they would already have violated the Fourth Amendment and any evidence they obtained would be inadmissible, whether found advertently or inadvertently. The Court hoped this requirement would replace attempts to judge the admissibility of evidence based on trying to determine what a police officer's expectations were while performing a lawful search.

However, Justices Brennan and Marshall dissented, maintaining that the Fourth Amendment explicitly requires search warrants to describe the specific contents to be seized, which the majority overlooked. Nonetheless, despite the apparent liberties taken with the Fourth Amendment, Justice Stevens's view received the most support, and Horton v. California eliminated the inadvertence requirement. The majority argued that the new "plain view" doctrine relied on objective grounds for judging whether evidence not mentioned in a warrant can be permissibly seized, instead of on subjective grounds of trying to read the minds of the police to determine if the discovery of such evidence was truly inadvertent.

In this case the items seized from petitioner's home were discovered during a lawful search authorized by a valid warrant. When they were discovered, it was immediately apparent to the officer that they constituted incriminating evidence. He had probable cause, not [only] to search for the stolen property, but also to believe that the weapons and handguns had been used in the crime he was investigating.