Is a defendant entitled to a sua sponte instruction on mitigation of murder to voluntary manslaughter due to provocation?

Appellant claims he was also entitled to a sua sponte instruction on mitigation of murder to voluntary manslaughter due to provocation. Under Horn, voluntary manslaughter instructions are appropriate in a prosecution for conspiracy to commit murder where there is some question regarding the individual defendant's capacity to harbor the mental state of malice at the time of his entry into the conspiracy. (People v. Horn, supra, 12 Cal.3d 290, 300-301, 115 Cal.Rptr. 516, 524 P.2d 1300.) Here, there was no evidence suggesting any provocation directed at appellant. Hence the court was under no duty to deliver voluntary manslaughter instructions.