Is an investigative stop valid under the Fourth Amendment?

"It is well established that certain temporary seizures short of arrest based upon probable cause are justifiable under the Fourth Amendment where the officer subjectively has a reasonable and articulable suspicion based upon objective facts that the person to be detained is involved in crime which has occurred, is occurring, or is about to occur. [Citations.]" (People v. Wilkins (1986) 186 Cal.App.3d 804, 808.) An investigative stop is valid if " 'the circumstances known or apparent to the officer . . . include specific and articulable facts causing him to suspect that (1) some activity relating to crime has taken place or is occurring or about to occur, and (2) the person he intends to stop or detain is involved in that activity.' [Citation.]" (People v. Perrusquia (2007) 150 Cal.App.4th 228, 233.)