Brian Coll, a former Rikers Island guard from Smithtown charged earlier this year with violating the civil rights of an inmate by brutally beating him, was accused in a new indictment Tuesday with causing the death of prisoner Ronald Spear.

Coll, 45, who previously faced up to 75 years in prison on civil rights and cover-up charges, now faces up to life in prison if convicted of causing Spear's death. He pleaded not guilty to the earlier charges.

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In a 2012 altercation in the Rikers medical unit set off by Spear's demands to see a doctor, prosecutors alleged Coll repeatedly kicked Spear in the head while he was restrained on the floor.

The inmate was declared dead shortly afterward. The new indictment claims his autopsy showed a "brain bleed" caused by blunt force impact to the head, and ruled the death a homicide caused by "hypertensive cardiovascular disease," with blunt force trauma and diabetes cited as "contributing factors."

Another Rikers guard from Long Island, Byron Taylor, 31, of Brentwood, also is charged in the case with helping to restrain Spear, conspiring in a cover-up and lying to a grand jury.