Amendment 4

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

This amendment guarantees the privacy of person, house, papers, and effects. This requires one (the law) to have probable cause or reasonable suspicion of a crime, a warrant by court, and the warrant being clear of all searches. 

Court cases:
Boyd v US (1886)- Established that the fourth amendment included that people cannot be forced to hold evidence against themselves.
Weeks v US (1914)- appealing conviction, running own lottery (federal marshals did not have warrant and was over turned).

Evidence in violation of the fourth amendment cannot be used in a criminal trial.

The video gives many examples of how the fourth amendment has been violated by law enforcement recently across the nation.