Olmstead v. United States

During the 1920s Prohibition era, several people led by Olmstead were involved in a bootlegging operation to import liquor from Canada.

Without a search warrant, police officers tapped into the telephone wires going into the suspects' homes. (The officers didn't enter the homes of the suspects.)

Over 5 months, the officers gathered evidence using the intercepted phone calls to Olmstead.

Olmstead and his associates were charged with violating the 18th Amendment & related Prohibition laws.

Olmstead moved to suppress the evidence under the 4th Amendment. The defendants were convicted at the federal trial.

Does interception of a person's private conversations (absent contact with the person's body, house, or personal property) constitute a 4th Amendment search or seizure?

No. 4th Amendment search or seizure doesn't occurs when officers secretly listen to a conversation so long as the officer has no physical contact with the person's body, house, or personal property.

Equivalently, a phone wiretap doesn't need a search warrant.

William Taft stated that the 4th Amendment right isn't violated by the officer's warrantless wiretapping of their private telephone conversations.

Louis Brandeis dissented; he likened the warrantless wiretapping to the un-authorized opening of the defendant's mail.