Is a failure to instruct on an instruction on attempted voluntary manslaughter prejudicial?

Even if the evidence supported the giving of an instruction on attempted voluntary manslaughter based on imperfect self-defense, we would conclude the error was not prejudicial. A trial court's failure to instruct on a lesser included offense is an error under California law (People v. Breverman (1998) 19 Cal.4th 142, 165, superseded by statute on another ground; People v. Watson (1956) 46 Cal.2d 818, 836); we may only reverse if defendant demonstrates a reasonable probability he would have achieved a more favorable verdict if the court provided the requested instruction. There are two reasons we cannot reach such a conclusion.