What are the requirements of a trial court to instruct sua sponte on a lesser included crime?

A trial court must instruct sua sponte on all lesser included offenses which find substantial support in the evidence. (People v. Breverman (1998) 19 Cal.4th 142, 162, 77 Cal.Rptr.2d 870, 960 P.2d 1094.) It must instruct on defenses which are supported by the evidence and which are not inconsistent with the defendant's theory of the case. (See People v. Barton (1995) 12 Cal.4th 186, 195, 47 Cal.Rptr.2d 569, 906 P.2d 531.) Substantial evidence exists where there is evidence from which a jury composed of reasonable persons could conclude that the defendant was guilty of the lesser crime. (People v. Breverman, supra, at pp. 162-164, 77 Cal.Rptr.2d 870, 960 P.2d 1094.) When assessing the sufficiency of evidence to warrant an instruction, we do not evaluate the credibility of witnesses, a task for the jury. (Ibid.)