A mistrial has been declared in a northeast Nebraska murder case. Cuming County jurors had heard nine days of testimony surrounding the second-degree murder and other charges against Derek Olson. Prosecutors say Olson and his father, Jody Olson, killed 64-year-old Ernest Warnock more than 2-years ago, at Warnock's home in Rosalie. The judge said the mistrial was warranted because a former Nebraska State Patrol investigator mentioned a lie detector test taken by Jody Olson. The judge says Jody