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

[t]here can be no doubt that an arrest permits some regulatory curtailment of liberty. Even before probable cause has been found by a neutral magistrate, "a policeman's on-the-scene assessment of probable cause provides legal justification for arresting a person suspected of crime, and for a brief period of detention to take the administrative steps incident to arrest." Gerstein v. Pugh, 420 U.S. 103, 113-14 [95 S.Ct. 854, 863, 43 L.Ed.2d 54] (1975). In addition, a seizure "reasonable" under the Fourth Amendment permits detention until a determination of probable cause by a judicial officer "promptly after arrest." Id. at 125 [95 S.Ct. at 868]. Furthermore, the Constitution's scheme for a system of criminal justice specifies that arrest is to be followed by trial and plainly implies that reasonable steps may be taken to ensure that the trial will take place. Procedures may therefore be used both to secure the defendant's presence at trial and to prevent the defendant from aborting the trial by intimidating witnesses or physically harming them.... Pretrial detention to avoid undue risks of flight or jeopardy to the trial process [is] not prohibited by a constitutional scheme that relies on the trial process to determine guilt and enforce the criminal law.