The U.S. Supreme Court has held that police officers are not required to delay in the course of an investigation if to do so would gravely endanger their lives or the lives of others. In addition, under such conditions the Court has applied a 'reasonable suspicion' standard of proof. Many warrantless searches of premises and seizures involve the suspected presence of an armed and dangerous person. Suspicion that a life-threatening emergency is present also will justify an emergency search or seizure based upon threat to life. Under certain circumstances, police may find it necessary to search one place so that rescue can be performed elsewhere. As with other emergency searches involving threat to life, such intrusions must be limited by its justification and can be no greater than needed to obtain the information. Several special circumstances that may justify limited warrantless intrusions include those required for the execution of a search warrant, for monitoring arrestees, and in cases of suspected threat to nonhuman life. 66 footnotes.