A search for rapists let off by court mainly reveals articles about a case in Scotland where a young man escaped prison, which is entirely due to the SNP. I would imagine you are referring to cases where juries have returned not guilty verdicts where you think it should have been guilty. Of course, you only have the limited summaries produced in the press, whereas the jury will have heard all the evidence. But hey, let's not bother with evidence and proof.
Juries are not perfect. They sometimes get it wrong and find someone not guilty when really, on the evidence, they should be found guilty, just as they sometimes convict innocent defendants. But they are the best we have, and they convict in around 60-65% of rape cases. The main reason rape convictions are low is that many victims pull out of the process before it gets to court. That is what needs to be addressed.
And, of course, none of this has anything to do with the subject of this thread - a young woman who, on the evidence, murdered a man who was not a child sex abuser, as you implied and another alleged. It is clear from the evidence that she was not acting in self-defence. She was acting out of anger.