Prosecutors won't file criminal charges against six Denver sheriff's deputies in the death of a jail inmate who suffocated while being restrained.

District Attorney Mitch Morrissey said Thursday the deputies used necessary force to restrain 50-year-old Michael Marshall during the Nov. 11 encounter.

Morrissey says deputies restrained Marshall in a prone position for several minutes after he became aggressive toward another inmate and ignored commands. His family removed him from life support nine days later.

A medical examiner said Marshall was suffering a psychotic episode. His death was ruled a homicide.

Morrissey says the deputies didn't intend to hurt Marshall. He says the case is an example of the difficulties of dealing with the mentally ill.

It comes as the troubled agency tries to reform after a series of misconduct and excessive force allegations.