If they have probable cause to believe that a crime has been committed or that there is evidence of criminal activity, offices can obtain a search warrant from a judge. The search warrant empowers them to enter onto private property, by force, if necessary. Once there, they can search for the items or individuals specified in the warrant, and seize them if found.

Search warrants can also be issued to obtain information from persons or institutions who are not participants in the crime. This information can include banking and phone records, medical records, or any other information that may provide evidence of a crime. In limited cases, phone taps and other methods of electronic surveillance may be used. These require close supervision by the courts because they also affect the rights of all the innocent persons with whom the suspect deals.