How have the courts interpreted section 12021 of the California Criminal Code when a defendant is charged with possession of a firearm by a felon?

Defendant contends that the trial court erred by allowing the prosecution to impeach him with a crime erroneously called "possession of a firearm by a felon." Under the same heading, defendant also contends: that a juvenile cannot be a felon, and thus his juvenile offense was not a proper basis for him to be "a felon in possession of a firearm"; that the trial court abused its discretion in failing to "sanitize" the prior conviction so that its similarity to the current charge (count 6) would not be revealed to the jury; and that a violation of subdivision (d) of section 12021 does not meet the test of a crime of moral turpitude, as enunciated in People v. Castro (1985) 38 Cal.3d 301.