What is the test for instructing a jury on a lesser included crime?

question as to whether the greater, charged crime has been proven and there is substantial evidence that only a lesser included crime was committed. If the trial court fails to instruct on the lesser included offense, we reverse only if, after considering the entire record, we find a reasonable probability that the error affected the outcome of the trial. (People v. Breverman (1998) 19 Cal.4th 142, 154, 165.) However, the existence of any evidence " 'no matter how weak' " will not justify instructions on a lesser included offense. (Id. at p. 162.) Instead, such instructions are required only if the evidence that defendant is guilty of the lesser offense is " 'substantial enough to merit consideration' " by the jury. (Ibid.)