What is the test for reasonable detention under the Fourth Amendment?

"The Fourth Amendment to the United States Constitution prohibits seizures of persons, including brief investigative stops, when they are 'unreasonable.' [Citations.]" (People v. Souza (1994) 9 Cal.4th 224, 229.) For a detention to be reasonable, "the circumstances known or apparent to the officer must 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. Not only must he subjectively entertain such a suspicion, but it must be objectively reasonable for him to do so: the facts must be such as would cause any reasonable police officer in a like position, drawing when appropriate on his training

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