Amos v. United States
In Amos v. United States, 255 U.S. 313 (1921), IRS agents found a woman at home, identified themselves, and told her they had come to search. She opened the door, whereupon the officers entered and searched. Id. at 315.
The Court held that "under the implied coercion here presented, no ... waiver was intended or effected." Id. at 317.