[T]he police officer must be able to point to specific and articulable facts which, taken together with rational inferences from those facts, reasonably warrant that intrusion. 392 U.S. at p. 21.

[I]t is imperative that those facts be judged against an objective standard: would the facts available to the officer at the moment of the seizure or search “warrant a man of reasonable caution in the belief” that the action taken was appropriate? 392 U.S. at pp. 21-22, cites omitted.

[A] police officer may, in appropriate circumstances and in an appropriate manner, approach a person for purposes of investigating possibly criminal behavior even though there is no probable cause to make an arrest. 392 U.S. at p. 22,

A detention is reasonable under the Fourth Amendment when the detaining officer can point to specific and articulable facts that, considered in light of the totality of the circumstances, provide some objective manifestation that the person detained may be involved in criminal activity. 9 Cal.4th at p. 231, underline added.

“[R]easonable suspicion [is] a standard less demanding than probable cause not only in the sense that reasonable suspicion can be established with information that is different in quantity or content than that required to establish probable cause, but also in the sense that reasonable suspicion can arise from information that is less reliable than that required to show probable cause.” 9 Cal.4th a pp. 230-231.

The possibility of an innocent explanation does not deprive the officer of the capacity to entertain a reasonable suspicion of criminal conduct. Indeed, the principal function of [police] investigation is to resolve that very ambiguity and establish whether the activity is in fact legal or illegal. In re Tony C., 21 Cal.3d at p. 894, and People v. Souza, 9 Cal.4th at p. 233, underline added.

Terry [v. Ohio] accepts the risk that officers may stop innocent people. Indeed, the Fourth Amendment accepts that risk in connection with more drastic police action; persons arrested and detained on probable cause to believe they have committed a crime may turn out to be innocent.

Residents of neighborhoods are in the best position to monitor activity on the streets. But residents, also fearful of the consequences, may not always wish to identify themselves and volunteer their names. According no weight as a matter of law to such anonymous tips would only discourage concerned residents from even calling the police, would burden the rights of ordinary citizens to live in their neighborhoods without fear and intimidation, and would render citizens helpless in their efforts to restore safety and sanctity to their homes and communities. 40 Cal.4th at p. 468.

Our decisions make clear that questions concerning a suspect’s identity are a routine and accepted part of many Terry [v. Ohio] stops. ... If there are articulable facts supporting a reasonable suspicion that a person has committed a criminal offense, that person may be stopped in order to identify him, to question him briefly, or to detain him briefly while attempting to obtain additional information. A brief stop of a suspicious individual in order to determine his identity or to maintain the status quo momentarily while obtaining more information may be most reasonable in light of the facts known to the officer at the time. 159 L Ed 2d at pp. 302-303, internal cites and quotes omitted.

Knowledge of identity may inform an officer that a suspect is wanted for another offense, or has a record of violence or mental disorder. On the other hand, knowing identity may help clear a suspect and allow the police to concentrate their efforts elsewhere. 159 L Ed 2d at p. 303.

The principles of Terry permit a State to require a suspect to disclose his name in the course of a Terry stop. . . . The request for identity has an immediate relation to the purpose, rationale, and practical demands of a Terry stop. The threat of criminal sanction helps ensure that the request for identity does not become a legal nullity. 159 L Ed 2d at p. 304, underline added.

[A] Terry stop must be justified at its inception and reasonably related in scope to the circumstances which justified the initial stop. Under these principles, an officer may not arrest a suspect for failure to identify himself if the request for identification is not reasonably related to the circumstances justifying the stop. 159 L Ed 2d at p. 304, underline added.