Come on, think about it...

Doesn't everybody who is trying to tell whether he is the torturer/rapist realize that if Polanski didn't tell us for sure, then we cannot possibly know for sure, so it is a waste of time to try to know that.
What could be important then? If we were not told FOR SURE by the story that was told whether he was or was not that man, then there must be something else that we're supposed to get from this movie. From the first time I saw the movie I realized that Polanski (or Dorfman the playwright) wants us to take something else from this story. First of all, isn't it at least possible that the confession at the end was made up in such detail because he realized that if he didn't make it convincing then he would die right there? If any one of us is brought before the edge of that cliff and told that the person who has the power over us wants to hear something from us or else over the edge we go, then I for one am going to try to save my life. NOTHING else he said or did helped him --- she wanted a confession and NOTHING ELSE mattered to her. So, isn't it possible that he was not guilty? And, of course, on the flip side he could have finally been telling the truth and it took that much to get him to finally give it up. So, since we can't tell which is which because those telling the story (Polanski and/or Dorfman) have not made it obvious, then it has to be that they wanted to make a statement about so-called "kangaroo courts" that are totally biased and have no checks and balances. And that YOU CANNOT FIND THE TRUTH THAT WAY. Look, they checked his alibi by making a phone call, which is like calling a witness, but then since Sigourney Weaver's character felt that she was SO SURE IT WAS HIM, she dismissed the witness. Things like this go on in countries where a dictator has power, if someone speaks out against them, they are destroyed. And also, it could have been that he prepared that alibi in the event of something like this to protect himself because he is guilty.
So, don't you agree that it is fruitless to keep banging your head against the wall trying to figure if he is the one or not? There is an entirely different lesson to be learned, and it is way more fascinating than just finding out at the end if he is guilty or not.