In order to solve a crime, in many cases an investigator must perform a search of a suspect’s home, car or other area that the suspect has control over. The hope is that the search will turn up a key item or items linking the suspect to the crime.
That kind of search in the United States, however, must be done within legal boundaries.
The Fourth Amendment to the United States Constitution protects citizens from unreasonable searches but provides for search warrants issued by a judge or magistrate who is satisfied that there is sufficient “probable cause.”
A request for a search warrant must be supported by a police oath or affirmation describing the specific place to be searched and specific items to be seized. Each of the 50 states has a search warrant form, with some variation in wording depending on state search warrant statutes. There is also a federal search warrant form.
“Probable cause” as defined in several cases and most notably by the U.S. Supreme Court, is “a reasonable ground for belief, less than evidence justifying a conviction, but more than bare suspicion. Probable cause concerns circumstances in which a person of reasonable caution would believe an offense has been or is being committed.”
When a police detective believes there is sufficient probable cause in a criminal investigation, he or she prepares an affidavit and takes it to a judge. The affidavit’s purpose is to show the judge the detective’s reasons, or probable cause, to believe an object or objects related to the crime under investigation are at a specific place that needs to be searched.
In the affidavit, the detective must include personal observations, details of the investigation, hearsay received from other persons, and often information supplied by a reliable informant. Upon finding that probable cause exists, based on the sworn affidavit, the magistrate or judge signs the search warrant giving the detective the authority to conduct the search requested.