Penal Code section 12020, subdivision (a)(1) is not a public welfare offense, and requires that the prosecutor prove that the possessor of a weapon know of the weapon’s illegal characteristics. Where the prohibited weapon is a “short-barreled rifle,” as in this case, where the rifle has been altered to reduce its overall length to less than 26 inches, the prosecution must establish the defendant’s knowledge of the shortness of the rifle, not its precise dimensions. The appellate court in this case held that the trial court’s failure to instruct on knowledge required reversal of the defendant’s conviction because the evidence was in conflict as to whether defendant knew that the rifle was shorter than the 26 inches specified in the statute. The Supreme Court reversed the judgment of the Court of Appeal because the uncontested evidence established appellant’s knowledge of the weapon’s shortness caused by it having been sawed-off. The trial court’s failure to instruct the jury that the defendant’s knowledge of the rifle’s illegal characteristic was an element of the crime charged was harmless under any standard.