Many people think that once law enforcement has a warrant they can do whatever they want. That is, if police search your home or business with a warrant that they can search everywhere.
Evidence obtained by the government to be used against you at trial must be obtained without violating your rights. In the home search context, this usually requires a warrant. But the warrant itself must also be constitutional.
For a warrant to be valid it must be based on probable cause, it must be issued by a neutral and detached magistrate, and it must describe with particularity the things and places to be searched. Courts enforce these three requirements very strictly.
For example, the judge handling ex-football player Aaron Hernandez's case just recently excluded evidence due to an inadequate affidavit. An affidavit is the sworn statement by a law enforcement official attached to a search warrant that forms the basis of why a judge should issue the warrant. The affidavit provides the probable cause and it states with particularity what is to be searched and where.
In the Hernandez case, this means that prosecutors can’t use .45-caliber bullets and a .45-caliber magazine found in Hernandez’s apartment and car at this trial for murder. "Though the search was pursuant to a warrant, Garsh ruled that the affidavit supporting the warrant had 'absolutely no facts' that linked Hernandez 'in any way at all to the crime under investigation,'" according to the ABA journal.
In other words, if police do have a warrant and they searched your home, car, business and found incriminating evidence, such evidence should not be used against you at trial if the warrant was defective -- if it was not based on probable cause, not issued by a neutral judge or did not describe with particularity the places and things to be searched.