The question of whether a police search is legal can be a complicated matter. Even if a search warrant has been issued, the scope of the warrant is limited. Generally, a search warrant authorizes police to search for particular items of evidence in particular places. If investigators illegally search beyond the scope of the warrant, then evidence seized in the search may be kept out of court.
For example, a search warrant may give investigators permission to search an individual's office computer and, within that computer, certain kinds of files. If an investigator searches beyond those particular files without probable cause, then a defense attorney may be able to prove that the search was illegal.
Law enforcement officers are not allowed to search you or your property without probable cause, and generally a search warrant is needed to give police permission to search a person or private property. However, there are instances when police do not need a warrant to conduct a legal search.
For example, if police believe that a person has thrown a gun into a yard while being pursued on foot by an officer, then the police generally do not need a search warrant to step into the yard and retrieve the weapon. The gun would be seen as a danger to the community, so the police would have a right to seize the weapon.
Any person facing a criminal charge after a police search should speak with a criminal defense attorney about the available legal options. In some cases, it is possible to prove that investigators overstepped their authority in a search.