There are both intention and negligence in terms of mens rea of his instigators and a perpetrator who causing a traffic accident and his escape results in the victim’s death. They may constitute an accomplice under four conditions. According to interpretations of the Supreme Court, the instigators shall be joint offenders. However, generally, the mens rea of the perpetrator is negligence in traffic accident crime. What’s more, the traditional theory about the accomplice maintains that the mens rea of the offender is usually intention. Therefore, there is undoubtedly a difference between the theory and interpretation of Supreme Court. The use of behavior theory may help preferably understand mens rea of joint crime.