In the United States, exigent circumstances are circumstances that allow law enforcement to depart from established standards of practice. This term is most commonly used in reference to actions that would normally be seen as violations of the Fourth Amendment, which prohibits “unreasonable search and seizure.” There are other situations in which exigent circumstances can come into play, however.
Law enforcement officers who plan to rely on an exigent circumstances defense to explain behavior which would not otherwise be authorized need probable cause. This means that a reasonable person evaluating the same situation would have come to the conclusion that exigent circumstances were involved and that the law enforcement officer had to act. If probable cause cannot be proved, law enforcement can face penalties.
Emergency situations in which the life of a person, including a law enforcement officer, is threatened are examples of these kinds of circumstances. Likewise, if officers believe that evidence is about to be destroyed, that a situation comprises a threat to human health and safety, or that a situation would otherwise impede the ability to investigate a crime, they can claim exigent circumstances. This also applies to people like representatives of the fire department or an ambulance service.
A house fire is an example of exigent circumstances. Fire department personnel and police officers must be able to enter a residence in order to fight the fire and save the lives of people and animals who may be trapped inside. In this situation, it is not reasonable to wait for a warrant or verbal permission from the occupants to enter because people could be injured or killed. Likewise, police can enter a business with no warrant if there is a threat to health and safety, such as a gas leak.
Exigent circumstances also allow people to violate the knock and announce rule. When police are executing a legal warrant, they are usually required to knock, announce their presence, and verbally request permission to enter to execute the warrant. If they are denied, they can take other measures to execute the warrant. In exigent circumstances, such as a situation in which police fear that someone would be endangered if they announced that they had arrived, it is permissible to enter without knocking.