For as long as people have communicated via wires, other people have been finding ways to listen in on their communications. After the telegraph was invented in 1837 and the telephone in 1876, detectives like the Pinkertons quickly realized the usefulness of tapping phone lines, for reasons varying from personal to corporate espionage. States and government agencies like the Justice Department acted slowly in response to the phenomena, passing laws and regulations without consistency.
Olmstead sued, claiming his Fourth Amendment rights had been violated, the Supreme Court disagreed in a 5-4 decision. Chief Justice and former President William Howard Taft believed in a strict interpretation of the Fourth Amendment, one that could only rely on physical presence and sight. The telephone just didn't feature into the equation.
However, it was the dissent that truly lasted. Given by Justice Louis Brandeis, it begins to focus on the future in a way that sounds downright prophetic today. "The progress of science," Brandeis wrote, "in furnishing the Government with means of espionage is not likely to stop with wire-tapping. Ways may someday be developed by which the Government, without removing papers from secret drawers, can reproduce them in court, and by which it will be enabled to expose to a jury the most intimate occurrences of the home. Advances in the psychic and related sciences may bring means of exploring unexpressed beliefs, thoughts and emotions." more