Consent (as a term of jurisprudence) is a possible justification against civil
or criminal liability. Defendants who use this defense are arguing that they should not be held liable for an crime, since the actions in question were taken with the "victim's" consent and permission. For example, if one signs a document stating that one is aware of the hazards of paintball, and that individual is then injured playing the game; it is possible that the person who shot said individual cannot be held civilly liable.
Consent has also been used as a defense in cases involving accidental deaths, which occurred during sexual bondage. Time (May 23, 1988) referred to this latter example, as the "rough-sex defense".
In general, consent is not a defense against criminal liability. A defendant can argue that because of consent, there was no crime (for example arguing that the use of an automobile was not theft).
However, once a crime has been established consent is generally not a defense. For example, if a person intentionally puts someone's eye out, the fact that the victim has consented to the activity is generally irrelevant. The major exception to this is the crime of rape or sexual assault.
See also