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In any allegation of rape, the absence of consent to [ame="http://en.wikipedia.org/wiki/Sexual_intercourse"]sexual intercourse[/ame] on the part of the victim is critical. Consent need not be express, and may be implied from the context and from the relationship of the parties, but the absence of objection does not of itself constitute consent.
[ame="http://en.wikipedia.org/wiki/Duress"]Duress[/ame], in which the victim may be subject to or threatened by overwhelming force or violence, and which may result in absence of objection to intercourse, leads to the presumption of lack of consent. Duress may be actual or threatened force or [ame="http://en.wikipedia.org/wiki/Violence"]violence[/ame]. Even [ame="http://en.wikipedia.org/wiki/Blackmail"]blackmail[/ame] may constitute duress. The [ame="http://en.wikipedia.org/wiki/International_Criminal_Tribunal_for_Rwanda"]International Criminal Tribunal for Rwanda[/ame] in its landmark 1998 judgment used a definition of rape which did not use the word consent. It defined rape as: "a physical invasion of a sexual nature committed on a person
under circumstances which are coercive."
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Valid consent is also lacking if the victim lacks an actual capacity to give consent, as in the case of a victim with a [ame="http://en.wikipedia.org/wiki/Mental_impairment"]mental impairment[/ame] or [ame="http://en.wikipedia.org/wiki/Developmental_disability"]developmental disability[/ame], or is judgmentally impaired or incapacitated by [ame="http://en.wikipedia.org/wiki/Alcohol"]alcohol[/ame] or [ame="http://en.wikipedia.org/wiki/Drug"]drugs[/ame] (legal or otherwise).
Consent can always be withdrawn before the actual sexual intercourse takes place.
The law would invalidate consent in the case of sexual intercourse with a person below the age at which they can legally consent to such relations. (See [ame="http://en.wikipedia.org/wiki/Age_of_consent"]age of consent[/ame].) Such cases are sometimes called [ame="http://en.wikipedia.org/wiki/Statutory_rape"]statutory rape[/ame] or "unlawful sexual intercourse", regardless of whether it was [ame="http://en.wikipedia.org/wiki/Informed_consent"]consensual[/ame] or not.
In times gone by and in many countries still today marriage is said to constitute at least an implied consent to sexual intercourse. However, marriage in many countries today is no longer a defence to rape or assault. In some jurisdictions, a person cannot be found guilty of the rape of a spouse, either on the basis of "implied consent" or (in the case of former British colonies) because of a statutory requirement that the intercourse must have been "unlawful" (which is legal nomenclature for outside of wedlock).
[8] However, in many of those jurisdictions it is still possible to bring prosecutions for what is effectively rape by characterizing it as an assault.
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