BOSTON (AP) — The former University of Alabama-Huntsville professor sentenced to life in prison for killing three of her colleagues in a shooting rampage wants to go on trial in the 1986 death of her brother in Massachusetts, her lawyer said Tuesday.

Attorney Larry Tipton said Bishop wants to prove at trial that she had a "loving and caring relationship" with her brother and that the shooting was accidental.

In court documents filed Monday, Tipton said Bishop objects to a decision by Norfolk District Attorney Michael Morrissey to decline to prosecute her in the killing of 18-year-old Seth Bishop.

"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 has already received a sentence of life in prison without parole in the 2010 Alabama killings.

"The penalty we would seek for a first-degree murder conviction is already in place," he said.

Also, defense attorney Roy Miller, who represented Bishop in the Alabama shootings, said Tuesday that Alabama officials would be unlikely to let Bishop travel to Massachusetts even if a judge there cleared the way for a trial for her brother's death.

"It'll be a cold day in hell when Alabama releases Amy Bishop to go to Boston," he said. "This case is over."

Miller said he understands Bishop wanting to clear up the Massachusetts charges for the sake of her family, but her desires don't matter to authorities because she is serving a term of life without parole plus three other life sentences.

He said the charge filed in Seth Bishop's killing constantly "eats at" her. Bishop tried to kill herself by slashing her wrists in the Madison County jail in Alabama the night she was informed of the indictment in Massachusetts, he said.

"She's always claimed her innocence in that," Miller said. "She named one of her children after her brother. She loved him."

Morrissey said the indictment would be withdrawn "without prejudice," meaning he could reinstate it if something went wrong with the Alabama sentence, though he said he considered that unlikely.

Bishop claims 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.

In court documents, Tipton argued that inquest and grand jury proceedings that led to Amy Bishop's indictment in Seth Bishop's death were "one-sided" and tilted in favor of prosecutors. He said prosecutors would be unable to present evidence of a motive or intent by Bishop to kill her brother, while the defense would present evidence that she and her brother had a good relationship and credible evidence that she accidentally shot him.

Tipton said the shotgun has a documented history of malfunctioning and misfiring, evidence he said was discounted or ignored by authorities.

He also argues that Morrissey's plan to file a "nolle prosequi," or declaration that he does not intend to prosecute, is an "abuse of authority."

David Traub, a spokesman for Morrissey, said Bishop's filing of her objection "is legally meaningless."

Bishop, a Harvard-educated biologist, pleaded guilty to the Alabama shootings but the case had to go to trial because she had admitted to a capital murder charge. She was convicted at trial.

Bishop killed her boss, biology department chairman Gopi Padila, and professors Maria Ragland Davis and Adriel Johnson. Associate professor Joseph Leahy, staff aide Stephanie Monticciolo and assistant professor Luis Cruz-Vera were shot and wounded.