What is the test for a jury to convict a defendant of a lesser and necessarily included crime?

"Theft is a lesser and necessarily included offense in robbery; robbery has the additional element of a taking by force or fear. [Citations.] It is well settled that the trial court is obligated to instruct on necessarily included offenseseven without a requestwhen the evidence raises a question as to whether all of the elements of the charged offense are present and there is evidence that would justify a conviction of such a lesser offense." People v. Ramkeesoon (1985) 39 Cal.3d 346, 351.) "On the other hand, the court is not obliged to instruct on theories that have no such evidentiary support. . . . [] . . . [T]he existence of 'any evidence, no matter how weak" will not justify instructions on a lesser included offense, but such instructions are required whenever evidence that the defendant is guilty only of the lesser offense is 'substantial enough to merit consideration' by the jury. [Citations.] 'Substantial evidence' in this context is ' "evidence from which a jury composed of reasonable [persons] could . . . conclude[]" ' that the lesser offense, but not the greater, was committed." (People v. Breverman (1998) 19 Cal.4th 142, 162.) "In deciding whether there is substantial evidence of a lesser offense, courts should not evaluate the credibility of witnesses, a task for the jury." (Ibid.)

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