We actually know several things the jury does not know. For instance, the DA sought to have admitted emails from Nina to Hans that referred directly to overt threats Hans had made. They weren't allowed due to hearsay rules.
The "friend/lover" was not a serial killer. No professional who interviewed Sturgeon believes him. If they had, he would have been called to testify. The defense had the option of calling him; they chose not to, because they did not think he would help their case.
I find it ridiculous that the DA would have chosen to pursue a case against a lonely computer programmer instead of locking up a serial killer. You have to believe something pretty incredible to argue that Sturgeon was a real factor in this case.
