What kind of evidence should be required to prove sexual assault occurred?

Rape and abuse can often be proven; there can be physical evidence of it. But when it comes to an assault, especially one that happened many years ago, what kind of evidence is needed to prove it happened (beyond a reasonable doubt)? This is not just about Kavanaugh, but that was the inspiration, of course. There often will not ever be any hard evidence in a sexual assault case. Often it does come down to one person’s word against another. I keep hearing people say there’s “no evidence” that the assault occurred. Okay, so what would qualify as evidence? What piece of evidence would have to come forth to convince you? Or unless it’s physical evidence, should the claim of assault be thrown out?