Appellant’s youth was relevant at his Penal Code section 1172.6(d)(3) hearing to determine whether he had the mental state required for aiding and abetting implied malice murder, and trial court could not be presumed to have considered his youth. Appellant was 21 years old when he participated in a spontaneous attack with two minors, one of whom stabbed the victim to death, and he was convicted of second degree murder. He later filed a section 1172.6 petition and his (d)(3) hearing was held before any case had described the significance of youth to felony murder and before any case had applied those principles to a young adult. The trial court denied the petition and he appealed. Held: Reversed. The reasoning that requires consideration of youth in deciding guilt of felony murder also applies in determining the mental state of implied malice, which also requires proof that the defendant subjectively disregarded a known risk of death. At the time of appellant’s (d)(3) hearing, no court had yet applied that reasoning in the felony murder context or to a young adult. Thus, the Court of Appeal declined to find the matter forfeited and declined to presume that the trial court had considered appellant’s youth. The error was not harmless because factors present in the case, like intoxication, negative emotional arousal, and peer group influence, aligned with factors known to affect minor and young adult behavior.