Before Katz v. United States, a search under the Fourth Amendment required a trespass. If there was no trespass on one’s property, then there was no search. In Katz, a 1967 decision, the U.S. Supreme Court abandoned that approach, instead finding a search without a trespass based on the government’s invasion of a “reasonable expectation of privacy.” In Oliver v. United States, the Court found that trespass was not sufficient to create a search. It found no reasonable expectation of privacy in open fields, and thus no search, even though the defendant had erected “No Trespassing” signs around his property to exclude the public, consistent with state law. After Oliver, it seemed clear that trespass no longer equaled a search.
In United States v. Jones, the latest case on Fourth Amendment searches, the Court returned to trespass as a bar on warrantless searches. It held that attaching an electronic tracking device to an individual’s car constituted a search. Because attaching the device constituted a trespass, it was a search and the government was required to obtain a warrant. The majority opinion and concurrences duel on whether reviving trespass in Fourth Amendment jurisprudence is wise, but all agree on the historical point that landowners always had the right to sue for trespasses on their property, including on open fields.