A U.S. military policeman who was beaten by fellow MPs during a botched training drill at the Guantanamo Bay, Cuba, prison for detainees has sued the Pentagon for $15 million, alleging that the incident violated his constitutional rights.

Spec. Sean D. Baker, 38, was assaulted in January 2003 after he volunteered to wear an orange jumpsuit and portray an uncooperative detainee. Baker said the MPs, who were told that he was an unruly detainee who had assaulted an American sergeant, inflicted a beating that resulted in a traumatic brain injury.

Baker, a Persian Gulf War veteran who re-enlisted following the Sept. 11 terror attacks, was medically retired in April 2004. He said the assault left him with seizures, blackouts, headaches, insomnia and other psychological problems.

In the lawsuit filed in U.S. District Court in Lexington, Ky., Baker demanded reinstatement in the Army in a position that would accommodate his medical disability. He said the Army put him on medical retirement against his wishes.

A Pentagon spokeswoman declined to comment, saying she could not discuss pending litigation.

The Pentagon first said that Baker’s hospitalization following the training incident was not related to the beating. Later, officials conceded that he was treated for injuries suffered when a five-man MP “internal reaction force” choked him, slammed his head several times against a concrete floor and sprayed him with pepper gas.

No one has been disciplined or punished for the assault, said Baker’s lawyer, T. Bruce Simpson Jr.