It depends. Your counsel would have to object at that time to preserve the record. However, if the court refused argument on the instruction, or even a sidebar discussion, that could be potential grounds.
If he has any record, there may be complications. You did not say what he was charged with, ie just holding, intent to sell etc. What Penal Code section(s) are involved? Contact counsel in the area and discuss with them. I am guessing you are in Fontana or SB? He definitely needs an attorney.