In California v. Roy, U.S. 117 S. Ct. 337 (1996) (per curiam), the Supreme Court characterized "an error in the instruction that defined the crime" as a trial error rather than a structural error. In that case, the defendant was accused of aiding a confederate in committing first-degree murder. See id. at 117 S.Ct. at 337. The trial court had instructed the jury the defendant could be convicted if it found beyond a reasonable doubt that he had knowledge of his cohort's unlawful purpose and that the defendant aided him in the commission of the act. See id. at 117 S.Ct. at 337-38. The instruction was erroneous under state law because it failed to convey the critical idea that the defendant must also have intended to aid in the commission of the crime in order to be found guilty. See id. at 117 S.Ct. at 338.