– Jessica Schaffhausen sat in a courtroom and quietly cried as her ex-husband softly delivered the words that many had been waiting to hear: "Guilty ... Guilty ... Guilty."

One after another Thursday, Aaron Schaffhausen admitted to killing their three daughters, 11-year old Amara, 8-year-old Sophie and 5-year-old Cecilia, in their River Falls home in July. It was a case one county prosecutor called the worst he'd ever seen.

Aaron Schaffhausen is still arguing that he should not be held responsible for the crimes, though, because of mental illness. His attorneys will attempt to prove that to a jury starting next week.

Defense attorney John Kucinski said after the hearing that his client decided to plead guilty to the crimes so they could get right to the heart of the matter: mental health.

"We just figured, well, let's get to the issue, I guess," Kucinski said.

Prosecutors had been poised to show a jury a stream of evidence that Aaron Schaffhausen cut his daughters' throats, tried to set fire to the house where the girls lived with his ex-wife and phoned his ex-wife, saying he had killed their daughters on the afternoon of July 10.

They alleged that Schaffhausen, who was working a construction job in Minot, N.D., showed up near River Falls unexpectedly that day and asked his ex-wife if he could see the girls. She agreed but insisted that he leave the house before she returned home from work at 3:30 p.m.

When he arrived, the girls were excited to see their father and pulled him upstairs to show him their things, their baby sitter told authorities, according to court papers. She left soon afterward.

At 3:30 p.m., Jessica Schaffhausen answered her phone. "You can come home now, because I killed the kids," her ex-husband told her, according to charges.

Police found each girl in her own bed, a blanket drawn up to her neck, dried blood on her face.

Wanted to hear him

Victim advocates whisked Jessica Schaffhausen out of the courtroom after Thursday's hearing. Her uncle Flint Watt later said by phone that their family is satisfied with the progress of the case so far.

"In some ways it might make it easier for family members to not have to have all the details come out in a trial about guilt," Watt said.

In the courtroom just before the plea, Jessica Schaffhausen paged through photos of the girls on her cellphone. Women sitting next to her put their arms around her.

"I think she wanted to hear him admit that he had done what he did," her uncle said.

Asked how she was faring, he said: "She's had her tough times, but she's an amazingly tough woman."

There was no plea agreement with prosecutors, and St. Croix County Circuit Judge Howard Cameron made it clear to Schaffhausen that there were no guarantees as to what kind of sentence he might get.

Under the guilty pleas to first-degree intentional homicide, Schaffhausen faces a sentence of life in prison for each death. If he convinces a jury that he was insane, he would be sent to a mental institution.

Proving insanity

Next week's trial is likely to contain a flurry of mental health research and conclusions. Experts for the defense, the prosecution and the court have each examined the defendant.

To win an insanity claim, defense attorneys will specifically need to prove that Schaffhausen had a mental disease or defect at the time of the crimes and that because of that, he lacked "substantial capacity" either to appreciate the wrongfulness of his conduct or to conform his conduct to the law.

Although the defense has to prove insanity by a preponderance of evidence, not the more difficult standard of beyond a reasonable doubt, Wisconsin legal experts said it's a difficult claim to win.

Prosecutors, who had more than 100 people on their witness list, are still likely to introduce a great deal of evidence about the actual crimes, trying to show that Schaffhausen planned them and then tried to cover them up.

They will likely highlight the deliberate steps Schaffhausen is accused of taking — getting a knife, cutting each daughter's throat, tucking them into bed and calling his ex-wife — to show that he wasn't acting impulsively and knew that what he was doing was wrong, said Daniel Blinka, Marquette University law professor.

The defense is likely to argue: "Look at what happened here. How can this guy not be nuts?" Blinka said.

Though experts help a jury make sense of mental illness, "we tell the jury that they're not bound by medical labels," Blinka said. "It's a community standard, really, as to what is a mental disease or defect."

While the public is quick to say someone who committed horrendous crimes has to be mentally ill, University of Wisconsin law Prof. Keith Findley said it comes down to a jury determining whether a defendant just couldn't comprehend that what he was doing was wrong, or if he did understand it was wrong, he lacked the ability to control himself.

"It's hard to satisfy juries to absolve somebody of responsibility when they've done something wrong and something serious," Findley said. "But it does happen and it's there for a reason, because the law has made a judgment that we don't want to punish people for being sick."

Nothing but sadness

If, after the insanity trial, 10 out of 12 jurors agree that Aaron Schaffhausen was mentally ill and not responsible for the crimes, he would be committed to a mental institution, attorneys said.

Kucinski said after Thursday's hearing that his client "would like to end up in a mental health institute so he can understand how this could have ever happened to him and his girls."

In questioning his decision to plead Thursday, Aaron Schaffhausen was asked in court whether he was receiving mental health treatment in jail, where he is on suicide watch.

Schaffhausen responded: "I would like to have treatment, but it would have been used by the prosecution so I chose not to, under the advice of my attorney."

Prosecutor Gary Freyberg said after the hearing that Schaffhausen has refused to speak to jail authorities on the advice of his attorney, so jail officials are compelled to keep him separate from other inmates and on suicide watch.

Kucinski said his client "has a lot of remorse. He's depressed. He's been depressed for a long time."

Kucinski, who expects anywhere from 20 to 50 witnesses for the trial, said he was shocked the judge didn't agree to move the trial to another county.

"For this whole community, it's a very sad thing, isn't it? There's absolutely no winners in this," Kucinski said. "There's nothing that comes out of this but sadness, is there ... three young beautiful girls, they're all deceased now."

Along with the murder pleas, Aaron Schaffhausen pleaded guilty to attempted arson.