Radley Balko has a friend who “doesn't think our criminal justice system is capable of handling rape, given that it’s so often a he said/she said thing, and that the results for both parties are so damning.” I think there’s something to this. The difficulty with rape as a crime is that it depends crucially on a single mental event: consent, an ephemeral phenomenon that takes place entirely within the mind. There is no unambiguous physical evidence of consent, because consent (or the lack thereof) can coexist with all sorts of physical circumstances. For the prosecution, even bruises and scratches aren’t good enough – some people like it rough. For the defense, clear and apparent sexual interest by the victim isn’t good enough – she can change her mind any time.
It might be objected that other crimes are like this, too. In a legal system largely based on individual rights and choice, consent is always of the essence, and consent is always ephemeral. Maybe the battery victim was actually a masochist who asked for it. Maybe Sears didn’t really want to keep that television, and didn’t mind that hoodlum walking out with it. But in those cases, while we can construct the hypotheticals, they just aren’t very plausible most of the time. The overwhelming majority of people aren’t masochists, and profit-maximizing firms don’t generally give away their products for free. To get away with these claims, the defense would have to adduce some strong evidence – e.g., the victim’s previous sado-masochistic relationships, or Sears’s advertising campaign in which it promised to give TVs to 10 lucky winners. Otherwise, the strong presumption is against consent. In the case of rape, however, no such strong presumption of non-consent applies: people give away sex for free all the time.
Furthermore, in other kinds of case, all sorts of circumstantial evidence can be introduced in court. Murder motives are not just allowed but welcomed. If the alleged assault victim had prior sado-masochistic relationships, we’d like the jury to know it. While the issue is still one of consent, we accept a variety of historical indicators of whether a specific person would or wouldn’t have been likely to give such consent, or would or wouldn’t have been likely to violate someone else’s rights. With regard to rape, however, we have moved progressively in the other direction, at least with respect to the interests of victims. Many states have “rape-shield” laws that specifically prohibit any evidence regarding the previous sexual history of the alleged victim. Why? Because no matter what she did in the past, she has the ability and the right to change her behavior in the present, and maybe she did. Of course, the same is true of the alleged rapist, though evidence of his previous history is often allowed – read this fascinating op-ed on that subject.
Perhaps the law is justified in keeping out character evidence in rape cases because of the peculiar nature of the crime, though it’s rather hard to justify allowing such evidence to be introduced only in support of one party. Nonetheless, the more we move in the direction of ruling out all evidence of character and history that is not directly related to the specific event, the more we will be casting about fruitlessly trying to find physical evidence of a non-physical event.