Amendment IV:
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 probably cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
Ok, that's a mouthful. Basically what this means is that cops can't just bust into your house and take your shit. When this amendment was ratified the British troops could just burst into one's home, take his shit, destroy his personal papers and important documents and if he resisted he'd be thrown into jail or shipped off to van dieman's land (Australia) We as americans were sick of it. So we made sure that we had protection against such a disastrous activity. It's why the cops have to go to a judge to get a search warrant.
