Although police can make "warrantless arrests"--arrests made without a warrant when they witness a crime, for example, or when there is probable cause to believe a suspect committed a felony--officers often go through a set of steps to obtain an arrest warrant for suspects. The steps to getting a warrant for a suspect's arrest rarely vary and are much like those used in obtaining a search warrant. Police generally need a warrant to enter a suspect's home in non-emergency situations.
Establish "probable cause," which is a reasonable belief that a person committed a crime. Probable cause is rooted in the Fourth Amendment, which states, "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."
Submit a written affidavit, under oath, to a judge. The affidavit should contain all evidence that supports probable cause for the arrest, including what led an officer to believe that a particular person committed a crime. Probable cause can be established through witness identification, DNA, fingerprint evidence or even hearsay from someone deemed "a reliable source." It cannot, however, be based on suspicion alone and is not enough to secure a conviction. The judge then determines whether the probable cause is valid and can issue the arrest warrant.
Check the facts about the suspect, including the spellings of names, addresses and other personal information. Although a suspect can dispute wrong information on an arrest warrant, including grammatical errors and misspellings, those alone are not enough to invalidate the warrant. A suspect must prove that he is not the person under suspicion.