I don't know. It also doesn't say whether or not that was allowed in both trials. If I were the judge, I would have ordered a new trial and had that "evidence" withheld (not sure if that can be done).
What is at question is whether or not the woman was legally insane when the crime took place. It appears the defense offered compelling evidence to support that she was, did the prosecution offer anything to counter that? If they didn't, then yes I agree that it should be overturned.
Now, if the prosecution DID offer evidence that she was not insane, that she knew the difference between right and wrong and instead committed this crime out of malice, then, and I can't believe I am saying this, I agree with CR90. If credible evidence was offered by the prosecution to counter the claim of insanity by the defense OR the evidence submitted by the defense to support that claim was not not compelling, then no judge should overrule a jury's verdict.
Edit: Let me clarify, I do not agree with the way CR90 is making his argument, he seems incapable of making any sort of valid point. I only mean that I would agree that the judge should not have overturned this particular verdict if those conditions were met. That said I am still entering myself into Monster Fail just for having typed those words.