ROCKLAND — A Maine State Prison inmate serving 45 years for killing a woman in 1999 is claiming self-defense in the death of another inmate.

Fifty-year-old Franklin Higgins went on trial Monday in Rockland in connection with the death of Lloyd Millett, who was serving a life sentence for strangling two women over a weekend in 1995 while working as a farmhand in Turner.

Higgins was originally indicted for murder, but prosecutors revised the charge to aggravated attempted murder after an autopsy showed health issues may have contributed to Millett’s death.

Prosecutors say Higgins struck Millett with a vice clamp in the prison workshop on May 24, 2011. He died two weeks later.

Higgins’ attorney told jurors Monday that Higgins was acting in self-defense against the 300-pound Millett.