When a jury is given instructions on aiding and abetting and withdrawal of one who aids and abets a crime, what are the implications of this error?

Finally, the error in giving the aiding and abetting instructions was exacerbated by the court's reading of portions of the standard instructions applicable only to the natural and probable consequences doctrine and withdrawal of one who aids and abets a crime. When a trial court erroneously instructs the jury, "`the question we ask is whether there is a reasonable likelihood that the jury construed or applied the challenged instruction[s] in an objectionable fashion.' [Citation.]" (People v. Osband (1996) 13 Cal.4th 622, 679.) But where, as here, the instructions on aiding and abetting were not only unsupported by the evidence, but also referred to entirely inapplicable legal principles, it is difficult to apply the general presumption that "`jurors . . . understand and faithfully follow instructions.' [Citation.]" (People v. Smith (2007) 40 Cal.4th 483, 517-518.)