ROCKLAND — A Maine man already serving a 45-year prison sentence for killing a woman in 1999 has pleaded not guilty to charges connected to the death of another inmate.

Franklin Higgins entered not guilty pleas on Tuesday in Knox County Superior Court to two counts of aggravated attempted murder.

Lloyd Millett, another inmate at the Maine State Prison, died last June about two weeks after he was beaten.

According to court papers, the 45-year-old Higgins struck Millett in the head with a pipe clamp. Higgins was originally charged with murder, but prosecutors changed the charges because an autopsy showed there may have been other factors contributing to the 51-year-old Millett’s death.

Millett was in prison for killing two women in 1995.