(CBS/AP) BOSTON - Amy Bishop, the former University of Alabama-Huntsville professor sentenced to life for killing three colleagues in a shooting rampage, wants to go on trial in the 1986 death of her brother.
Bishop's lawyer filed court documents stating that she objects Norfolk District Attorney Michael Morrissey's decision to decline prosecuting her in the killing of 18-year-old Seth Bishop.
Attorney Larry Tipton said Amy Bishop wanted to prove at trial that she had a "loving and caring relationship" with her brother and that the shooting was accidental.
"She wants to use a trial to help demonstrate that she's innocent. She never intended to kill her brother," Tipton said Tuesday.
Morrissey said last week that he decided not to move forward with the murder indictment against Bishop because she already received a life sentence without parole in the 2010 Alabama killings.
"The penalty we would seek for a first-degree murder conviction is already in place," he said.
Bishop claimed she accidentally shot her brother while trying to unload her father's shotgun in the family's Braintree home. Bishop's mother, who witnessed the shooting, backed up her claim.
Authorities initially ruled the shooting accidental, but the investigation was re-opened after Bishop was charged with opening fire during a faculty meeting at the university in Feb. 2010, killing three of her co-workers and wounding three others.