Anissa Weier and Morgan Geyser, who were both aged 12 at the time of the attack, were charged as adults with first-degree intentional homicide on the attack on Payton Leutner, who was stabbed 19 times and left for dead in a park during a sleepover party.

Both girls faced up to 45 years in prison, if convicted. The teenagers entered an insanity plea.

Weier, now 15, pleaded guilty to attempted second-degree homicide as a party to a crime, with use of a deadly weapon.

The court was told that the victim's family supported the plea arrangement.

Weier will face a trial next month to establish the state of her mental health. If found guilty she could face up to 10 years in prison, however, if the jury found she was suffering mental illness at the time of the attempted killing, the 15-year-old will be sectioned to three years in a psychiatric hospital.

At the time of the attack, both girls told detectives they were acting to appease or impress Slender Man, an online urban legend the girls said they believed would harm them or their families if they didn't kill Leutner.

For the first time since her arrest, Weier, now a much more mature looking and sounding teenager, spoke at some length in court. She had to explain to the judge that she understood what she had done, and the consequences of pleading guilty to the new charge.

Weier also told the court for the first time that she feared Morgan Geyser, her co-defendant, would return to Waukesha and kill her if Weier didn't try to flee with her after the actual stabbing occurred.

Geyser pleased not guilty by reason of mental disease to attempted homicide chargers. Weier initially entered the same plea.

Luetner was found bleeding in a park by a passing cyclist. She was stabbed during a game of hide-and-seek after Geyser's 12th birthday sleepover the night before.

With Milwaukee Journal Sentinel