The police can get a search warrant from a judge if they have probable cause to believe that a crime is occurring at the property that they want to search or that the property contains evidence of a crime. “Probable cause” does not require a very high probability, despite the use of the word “probable.” (Read more here about what probable cause means.) The police will present an affidavit to the judge that outlines the justification for the warrant. It may contain not only their own impressions but also information that they obtained from trustworthy sources. If the judge is persuaded by the affidavit, they will issue a warrant that authorizes a search of the location for certain types of evidence.
An occupant of the home or other location being searched does not have the opportunity to contest a finding of probable cause before the search. Any challenge to the basis for a warrant will need to occur after the search. A successful challenge can result in the suppression of any evidence obtained through the unlawful search.
The Scope of a Warrant
The warrant will define the physical location that can be searched and the type of evidence for which the police are searching. If it limits the search to a certain area of the building, the police cannot search other areas. If it limits the search to drugs and related paraphernalia, the police cannot search for firearms or images of child pornography. The police sometimes have the right to seize illegal items or incriminating evidence that is not described in the warrant if they find it during a legitimate search for the evidence described in the warrant.
If the warrant limits the search to a certain person and their belongings, the police cannot search other people and their personal possessions without a separate justification based on probable cause. Having a reasonable suspicion that someone else is involved in a crime can justify a brief detention and possibly a frisk, but it will not justify a thorough search.
Any evidence found in a search that exceeds the scope of the warrant usually will be thrown out, unless an exception applies.
Exceptions to the Warrant Requirement
An exception to the warrant requirement may arise when the Fourth Amendment does not apply because there is no reasonable expectation of privacy. Or an exception may arise when certain circumstances justify the search. Perhaps the most obvious exception is when an item is in plain view, and the officer has a legitimate reason to be in a position to observe it. They cannot seize the item unless they have probable cause to believe that it is illegal or evidence of a crime.
One of the most complex exceptions is when the police receive consent to conduct a search from someone who has the authority to give valid consent. This usually means that they can conduct a search within the scope of that person’s consent, even if they do not have a warrant. Read more here about the consent exception.
Another exception involves searches incident to arrest and protective sweeps. Read more here about these types of searches. Similarly, there is an exception for stop and frisks when an officer has a reasonable suspicion that someone is involved in criminal activity, and the officer believes that they may be armed and dangerous. Read more here about stop and frisk searches. Finally, there is a general emergency exception that allows the police to conduct a search without a warrant if a delay would endanger public safety or cause vital evidence to be destroyed. Sometimes this arises when an officer is in “hot pursuit” of a fleeing suspect.