Under the Fourth Amendment to the United States Constitution, most searches by the police require a search warrant based on probable cause, although there are exceptions. Any police entry of an individual's home always requires a warrant (for either search or arrest), absent exigent circumstances, or the free and voluntary consent of a person with reasonably apparent use of or control over the property. Some commonly cited exigent circumstances are: hot pursuit of a felon (to prevent a felon's escape or ability to harm others); imminent destruction of evidence before a warrant can properly be obtained; emergency searches (such as where someone is heard screaming for help inside a dwelling); or a search incident to arrest (to mitigate the risk of harm to the arresting officers specifically).