HUDSON, Wis. (AP) -- A father changed his pleas Thursday to guilty but insane in the killings of his three young daughters last summer in Wisconsin, which means the defense at his trial will have to prove he had a mental disease or defect so severe that he wasn't responsible for his actions.
Aaron Schaffhausen, 35, had pleaded not guilty, but switched his plea after more than a day of delays and legal wrangling about what kind of evidence will be allowed at his trial, which starts next week.
Schaffhausen spoke in a flat tone that lacked emotion as he answered the judge's questions about his new pleas.
"Are you pleading guilty because you are guilty?" Judge Howard Cameron asked at one point.
"Yes," Schaffhausen responded.
With the plea change, prosecutors won't have to prove Schaffhausen killed his daughters and or that he tried to set fire to their River Falls home last July.
However, the defense will have to prove by a preponderance of the evidence that he had a mental disease or defect, and that he lacked substantial capacity to appreciate that what he did was wrong or couldn't control his impulses.
Jury selection is to begin Monday in St. Croix County Circuit Court.
Schaffhausen, who moved from River Falls and took a construction job in Minot, N.D., after his marriage broke up, is charged with three counts of first-degree intentional homicide and one count of attempted arson. Police found his daughters, 11-year-old Amara, 8-year-old Sophie and 5-year-old Cecilia, dead in their beds. Their throats had been slit, and gasoline had been poured in the basement.
Prosecutors allege Schaffhausen did it to get back at his ex-wife, Jessica, because he was bitter over their divorce and angry because he thought she had begun seeing another man.
According to the criminal complaint, Schaffhausen texted his ex-wife on July 10 to ask for an unscheduled visit with the girls, and she consented. Schaffhausen arrived and sent a baby sitter away.
About two hours later, he called his ex-wife and, according to the complaint, told her: "You can come home now because I killed the kids."
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