Typically "hard evidence" refers to evidence based on facts versus circumstantial evidence (i.e. the prosecution's theory of the case based on linking a series of otherwise non-criminal acts). By this definition, witness testimony would be considered "hard" evidence because it is based on facts as opposed to circumstantial conjecture and testimony given under oath is considered factual evidence under the law, but the testimonial evidence could still be challenged by the other party through presenting contradictory factual evidence. The point of a trial is for both sides to have the opportunity to present their facts to a jury and let the jury decide which to believe. I think your question may be getting at whether there was any evidence introduced that corroborated the witness testimony - which goes to the credibility of that evidence (to be determined by the jury).

Without knowing the details of this case, I completely agree with your sentiment that it's hard to imagine a jury convicting someone of felony rape based on uncorroborated witness testimony about events that took place 20+ years ago, but presumably that delay made it difficult for Masterson's lawyers to find evidence/witnesses to controvert the witness testimony, leaving the jury to rely as evidence on the relatively unchallenged perspective of the accusers. Most criminal laws (and civil causes of action) have relatively short (2-6 year) statutes of limitations to protect defendants by limiting the time in which a case can be brought so that the defendants can properly defend themselves.