HUDSON, Wis. - More than 100 jurors were whittled down to 15 on Monday in the triple murder case of Aaron Schaffhausen.
Lawyers eventually settled on 12 jurors and three alternates, comprised of nine women and six men.
Jury selection moved very slowly which was not a surprise to Minneapolis defense attorney Peter Wold.
"They are faced with the graphic nature of the deaths of innocent children," says Wold. "To say you can be fair, it's not easy for everybody to be able to do that."
Jurors should be spared the most graphic details because Schaffhausen is now admitting to killing his three young daughters in their River Falls home last summer.
Prosecutors say he slit the children's throats to get back at his ex-wife after a bitter divorce.
Schaffhausen changes his plea to guilty last Friday and is now arguing an insanity defense which means the case will take a more medical approach.
"There will be forensic psychologists, psychiatrists that can describe that, define it," says Wold.
Wold has argued insanity before and says even with doctors backing you up, it's tough.
"Mental illness is a very, very difficult subject for a lot of people," says Wold. "Getting jurors to understand that it is an excuse for an act, some people just aren't willing to do that."
In Wisconsin, an insanity plea does not need to be unanimous. The defense will only need to convince 10 of the 12 jurors that Schaffhausen is insane.
If they succeed, he will likely be committed to a mental health facility instead of prison.
The trial is expected to take several weeks.
Opening arguments begin Tuesday.
(Copyright 2013 by KARE. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)