Gregory Van Rybroek took the stand in a Waukesha County courtroom Thursday at Anissa Weier's trial.
Weier's plea agreement calls for her to spend at least three years in a Psychiatric Hospital, but a judge can increase the sentence pending an investigation.
A detective who interviewed a 12-year-old girl stabbed repeatedly in a Wisconsin park in 2014 has testified that one of two classmates accused of attacking her had been scaring her with stories about the fictional horror character Slender Man before the attack. Such a verdict would send Weier to a mental health facility instead of prison. She had faced up to 10 years in prison if she was found mentally fit.
He played segments of Weier's police interrogation in which she described a plot to kill Payton in order to become a proxy of Slender Man.
Weier had already pled guilty for her role in the stabbing.
"This was a delusion strong enough to kill for", defense lawyer Maura Ann McMahon said in her closing argument. "Anissa told [court-appointed psychologist Dr. Melissa Westendorf] that she didn't want Morgan to feel insane, so she said yeah", Waukesha County Deputy District Attorney Ted Szczupakiewicz said during closing arguments.
A total of 10 out of 12 jurors agreed on Friday that Weier had a mental disorder when she and her classmate Morgan Geyser stabbed their sixth-grade classmate 19 times.
"It comes down to did she have to or did she want to?"
Anissa Weier, now 15, had pleaded guilty in August to being a party to attempted second-degree homicide. "If adults have trouble distinguishing fake news, 12-year-olds will, because their brains can't yet discern or analyze as well".
"They knew this was wrong".
A psychologist testified during the trial, which started Monday, that Weier was suffering from shared delusional disorder. Weier and Geyser were arrested later that day and said they were walking to meet Slender Man in a northern Wisconsin forest.
Geyser has pleaded not guilty to being a party to first-degree attempted homicide.
Geyser's trial is scheduled to begin on October 16, the Milwaukee Journal Sentinel reported. Leutner may have died were it not for a bicyclist who found her after the attack. The stabbing victim, who Reuters has not named, survived the attack.