What is the current state of the law on warrantless searches under the Fourth Amendment?

"It is axiomatic that the 'physical entry of the home is the chief evil against which the wording of the Fourth Amendment is directed.' [Citation.]" (Welsh v. Wisconsin (1984) 466 U.S. 740, 748 [80 L.Ed.2d 732, 742].) "[W]arrants are generally required to search a person's home or his person unless 'the exigencies of the situation' make the needs of law enforcement so compelling that the warrantless search is objectively reasonable under the Fourth Amendment." (Mincey v. Arizona (1978) 437 U.S. 385, 393-394 [57 L.Ed.2d 290, 301].)