HUDSON, Wis. (AP) – A jury has been selected to hear the insanity trial of a man who admitted last week that he killed his three daughters in their River Falls home.  Thirty-five-year-old Aaron Schaffhausen pleaded guilty to three counts of first-degree intentional homicide, but he maintains he is not responsible because of a mental illness.  Prosecutors say Schaffhausen knew what he was doing last July when he killed 11-year-old Amara, 8-year-old Sophie and 5-year-old Cecilia.  A St. Croix County jury of nine women and six men were picked Monday to hear the case. Opening statements will begin Tuesday.  If Schaffhausen is found sane, he could spend the rest of his life in prison. If the jury finds he was not responsible, he could be committed to a psychiatric institution and possibly released someday.