If there routinely isn't enough evidence to convict an accused rapist, that would imply that the system isn't biased against the accused.

>There are 'rape shield laws' which is what I was referring to:

Sorry, I should have caught that. It appears this term refers to a bunch of different laws pertaining to rape cases in different jurisdictions. The general idea, that the victim's sexual history is not admissible evidence, makes sense to me. Whether or not the victim had multiple sexual partners or was promiscuous is irrelevant to the facts of the case, and serves only to hurt the victim's reputation. In many of these cases all we have to go on is the testimony of the accuser and the accused, so it is easy for these cases to devolve into character assassination. Obviously this has to be done in such a way that it does not infringe on the rights of the accused to mount a defense. Is there some specific provision in these laws you disagree with, or the entire concept?