More pieces of the puzzle are falling into place in Wednesday’s murder of a University of Iowa official. Police say 54-year-old Dr. Richard Nelson was stabbed to death by his wife, Phyllis, who is jailed on a charge of first-degree murder. The two were living apart — Dr. Nelson in a Cedar Rapids apartment and Mrs. Nelson in a large Iowa City home. Cedar Rapids police officer David Johnson says the motive is becoming clearer. He says they don’t know whey Mrs. Nelson went to the apartment, but says a domestic dispute resulted.Police won’t expand on the nature of the domestic dispute, but reports quote witnesses who say a woman in her 20s was led from the Cedar Rapids apartment by police after Dr. Nelson’s body was taken away by paramedics. U-of-I Dr. Nelson was executive dean of the U-of-I College of Medicine.