What is the case law on the aider/abettor's guilt in a murder case?

prosecution not involving felony murder or the natural and probable consequences doctrine, the aider/abettors guilt is based on the combined acts of all the principals and on the aider/abettors own knowledge and intent. Consequently, in some circumstances an aider/abettor may be culpable for a greater or lesser crime than the actual killer. ( People v. McCoy (2001) 25 Cal.4th 1111, 1120, 108 Cal.Rptr.2d 188, 24 P.3d 1210.)

[6 Cal.5th 918]