The Taft Court narrowly ruled 5–4 in Olmstead v. United States (1928) that wiretapping by federal prohibition officials did not violate the Fourth Amendment because listening to telephone conversations was not a search within the meaning of the Fourth Amendment. After listening to wiretaps for more than five months, government officials uncovered a large criminal enterprise, led by Roy Olmstead, involving the distribution of liquors. The government enlisted a telephone wiring expert to wiretap numerous telephone lines into the homes and offices of several individuals, including Olmstead.

Olmstead and others contended that the wiretaps constituted an illegal search and seizure, as they were done without a warrant and probable cause. However, Chief Justice Taft, in his majority opinion, found that the use of wiretaps did not constitute a search. He narrowly focused on the Fourth Amendment as protecting person’s tangible items from government inspection: “Here we have testimony only of voluntary conversations secretly overhead.”

He explained: “There was no searching. There was no seizure. The evidence was secured by the use of the sense of hearing and that only. There was no entry of the houses or offices of the defendants.” Taft believed that expanding the Fourth Amendment to protect telephone conversations would constitute an “enlarged and unusual meaning to the Fourth Amendment.”