A parent who hits or spanks his child will not be guilty of battery, provided that the purpose is to promote the welfare of the child, including preventing or punishing misconduct. Generally, the fact that the victim of a crime has consented does not bar criminal liability. First, some crimes are defined in such a way that lack of consent is an element of the crime . Second, for some crimes, in some courts, the fact that V has consented prevents D's conduct from constituting the harm from arising that the law is trying to prevent. Thus if the crime involves threatened or actual bodily harm , consent is a defense if the bodily harm is not serious or is part of a lawful athletic contest or competitive sport .
D strikes V repeatedly, trying to injure V, knowing that V is already hurt.
D will not be liable for battery, attempted murder, murder, or any other crime. Similarly, if the consent was obtained by fraud , it will generally not be valid. However, the fraud will negate the consent only where it goes to the essence of the harmful activity. The fact that V may have been contributorily negligent will not, by itself, be a defense to any crime. D's car slams into V's, killing him.