How does the Fourth Amendment protect privacy in the context of a hotel room search?

The Fourth Amendment protects people, not places. A person has a reasonable expectation of privacy no matter what his particular location. Governmental authorities may not invade that expectation absence exigent circumstances, without prior procurement of a warrant. Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L. Ed.2d 576 (1967). The difficulty in many cases will be in determining precisely what was the reasonable expectation of privacy of the individuals concerned, taking into account their particular environment.

The general rule is that information obtained by an officer using his natural senses, where the officer has a right to be where he is, is admissible evidence. The fact that the information is in the form of conversations emanting from a private space, such as a hotel room, is not a bar to its admissibility. Ponce v. Craven, 409 F.2d 621 (9th Cir. 1969). Furthermore, the fact that it may be necessary to place one's ear against a door in order to comprehend the conversations inside a room does not make the search unlawful. People v. Guerra, 21 Cal.App.3d 534, 98 Cal.Rptr. 627 (1971).