Aaron Schaffhausen, 35, has pleaded guilty but insane to three counts of intentional homicide and one count of attempted arson, according to Kare11.
Schaffhausen of River Falls was charged with the killings of his three daughters last summer. His defense will now have to prove he has a mental disease and could not control his actions, according to the Huffington Post.
The trial will begin on Monday. Schaffhausen is currently at the St. Croix County Jail, and is on suicide watch, according to Kare11.