Forty years ago, the Supreme Court's search incident to arrest doctrine was settled and relatively clear: as a routine matter, police could, without any particularized suspicion, search an arrestee for weapons and any evidence in his possession that the arrestee might try to conceal or destroy. The twin rationales justifying a search incident to arrest-officer safety and evidence preservationmarked the outer boundaries of police authority. In Schmerber v California, the Court explained that these two justifications "have little applicability with respect to searches involving intrusions beyond the body's surface." 1 According to Schmerber, "the interests in human dignity and privacy which the Fourth Amendment protects forbid any such intrusions on the mere chance that desired evidence might be obtained." 2 Thus, Schmerber required either a judicial warrant or some emergency that justified an exemption from the warrant requirement for the police to invade an arrestee's body. 3