Slender Man case: Shared delusion led 2 girls to stab a 12-year-old, expert reveals

WAUKESHA: A shared delusion and an interest in the paranormal led two girls to stab another 12-year-old girl in a Wisconsin park as a tribute to the fictional horror character Slender Man, a psychologist testified Wednesday.

Melissa Westendorf was appointed by a judge to evaluate one of the girls, Anissa Weier, now 15, after her insanity plea. Westendorf testified at Weier's mental capacity trial that she believes Weier suffered from a shared delusional disorder that left her unable to conform her conduct to the law when she and Morgan Geyser tried to kill their friend, Payton Leutner, in 2014.

Westendorf acknowledged under cross-examination that the condition is rare among two children who are friends. She said most cases involve spouses, a parent and child, or siblings. Weier's attorney, Joseph Smith Jr., asked why Weier, a good student, did not recognize that the belief in Slender Man and his powers to kill them or their families was a delusion.

"First of all, she was 12," Westendorf said, adding that Weier was influenced by a website focused on imaginary killers and boogeymen. "If adults have trouble distinguishing fake news, 12-year-olds will, because their brains can't yet discern or analyze as well."

Earlier, a detective who interviewed the victim after she was stabbed repeatedly and left for dead in a Waukesha park testified that Geyser had been scaring her beforehand with stories about characters from a horror website.

Leutner became so concerned about the stories Geyser was telling her that she asked her mother if they were real, Waukesha Police Detective Shelly Fisher said. Leutner told Fisher her mother tried to assure her it was all fiction, but she also told the detective that she still was uncertain and wanted to believe Geyser even after she stabbed her, the Milwaukee Journal Sentinel reported.

Jurors will determine whether Weier was mentally ill and therefore not criminally responsible at the time. Geyser, who did the actual stabbing, is scheduled to go on trial next month.

Weier told investigators she and Geyser believed they had to kill Leutner or else Slender Man would kill them and their families. Jurors saw clips Wednesday of investigators questioning Weier after the attack, during which Weier moved from apparent complete belief in Slender Man, to some doubt, to a realization by the end of her interrogation that she had been duped. "I know now it's just teenagers who really like scaring people and making them believe false things," Weier told Waukesha Detective Michelle Trussoni.

In his questioning of Trussoni, Assistant District Attorney Kevin Osborne focused on the fact Weier didn't clearly tell anyone she was afraid of Slender Man's wrath until after the stabbing, reinforcing his comments in opening statements Tuesday that Weier understood that what they were doing was wrong, but that she went along with the plot to preserve her friendship with Geyser.

Both Weier and Geyser were originally charged with being a party to attempted first-degree intentional homicide. Weier struck a deal with prosecutors in August in which she pleaded guilty to being a party to attempted second-degree intentional homicide, essentially acknowledging she committed all the elements of the offense. But she also pleaded not guilty due to mental illness or defect, setting up the trial on her mental status.

Geyser's trial is due to begin Oct. 9. She has also pleaded not guilty by reason of mental disease.