No means no, and in the eyes of the law, the relevant details of the specific incident at hand will be more important and influential in a case than a person's personal sexual history. That is to say, the law sees no difference between a promiscuous person and a celibate in terms of a rape attack.
That's paper law. Trial law is much different. A person's sexual history can be used to discredit the victim, to convince ordinary jurors, with ordinary opinions about promiscuity, to discount his/her testimony about being a victim of sexual assault. Rightly or wrongly, this tactic is often successful at getting an acquittal, or a hung jury mistrial.
I would argue that past sexual history cannot possibly be relevant to a person's ability to refuse sex on any particular occasion. Past sexual history might be relevant if the person has a sexual history with the accused, but even then, that history is not all-important.
The idea that a person (in particular a woman) cannot say "no" if she has led an "unchaste" life is archaic. It is perfectly logical that a woman could have had sex with one or more men in the past (without being married) and yet still reject the advances of another. The idea that a woman who has had multiple sexual partners in the past is in some way "fair game" is ludicrous. Therefore, I agree with rape shield laws that prevent an alleged rape victim from being questioned about her sexual history.
Let me first say that I agree with the initial response. Mostly. That said, I will offer the position that the devil's advocate would take.
A person's sexual history is absolutely relevant to PROVING his/her consent to sex on a given occasion. True, a promiscuous person has every right to refuse sex with anyone at any time. But consider that past events are the best predictor of future events and that a history of engaging in certain behavior will be a strong indicator of whether that behavior was engaged in on a given occasion.
As such, a person with a long history of engaging in consensual sex with multiple different partners should necessarily face increased scrutiny when that person accuses another of rape AND CONSENT IS AN ISSUE. Obviously, if the defendant claims the sexual activity never took place, or, if at the time the sexual activity was taking place, the defendant was threatening the victim with a weapon, consent is not an issue.
The victim's sexual history should be -A- piece of evidence that weighs upon whether or not they consented to sexual activity. A victim's history of accusing people of rape (especially when those accusations were ultimately found to be false) should be -A- piece of evidence that weighs upon the issue of consent. As should the victim's testimony. As should the victim's history, if any, of prostitution. As should the victim's history of blackmail or extortion. As should many, many other things.
Rape is an incredibly serious offense that carries with it DEVESTATING consequences. It is not unreasonable, in cases where guilt or innocence hangs on the victim's claim that the sexual activity was not consensual, to hold that victim's past actions against him/her in an effort to find the truth. True, this will inevitably have the effect of disencouraging legitimate victims to come forward for fear of public shame. True this will also inevitably result in some guilty people going free. But in America, we hold the prosecution to an extremely high standard (proving guilt beyond a reasonable doubt), and although it is not the defendant's job to prove his/her own innocence, eviscerating their ability to do so through rape-shield laws is in derogation of the system we claim to support.