How have courts interpreted "substantial evidence" in the context of jury instructions on a lesser included offence?

(People v. Breverman (1998) 19 Cal.4th 142, 162 (Breverman).) "[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." (Ibid.) "'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." (Ibid.; People v. Barton (1995) 12 Cal.4th 186, 201, fn. 8.)