(b) Consent to bodily injury.–When conduct is charged to constitute an offense because it causes or threatens bodily injury, consent to such conduct or to the infliction of such injury is a defense if:
(1) it is given by a person who is legally incapacitated to authorize the conduct charged to constitute the offense;
(2) it is given by a person who by reason of youth, mental disease or defect or intoxication is manifestly unable or known by the actor to be unable to make a reasonable judgment as to the nature or harmfulness of the conduct charged to constitute the offense;
(3) it is given by a person whose improvident consent is sought to be prevented by the law defining the offense; or
(4) it is induced by force, duress or deception of a kind sought to be prevented by the law defining the offense.