CHICAGO (Reuters) - A former police officer from St. Louis, Missouri, was sentenced on Thursday by a federal judge to four years and four months in prison for assaulting a handcuffed man and injuring him by forcing a gun into his mouth, federal prosecutors said.

The ex-policeman, Thomas Carroll, 52, had pleaded guilty to a charge of violating the civil rights of the victim, identified by his initials, M.W., according to a statement from the U.S. Justice Department.

The sentencing came at a time of a growing national movement to hold police more accountable for misconduct and especially for the use of lethal force against minorities. The Justice Department did not provide the races of the two men, but the St. Louis Post Dispatch newspaper reported that both Carroll and M.W. are white.

The case arose from an incident in July 2014, when the man identified as M.W. was picked up by police for being in possession of a credit card that was allegedly stolen from Carroll's daughter.

Later, during an interrogation at a police station, Carroll threw M.W. against a wall, punched him, and shoved his gun in his mouth, chipping his teeth and bloodying his lip, according to evidence presented by prosecutors at the plea and sentencing hearings before U.S. District Judge Henry Autrey in Saint Louis.

Alleged civil rights abuses by law enforcement are investigated and prosecuted by the Justice Department's Civil Rights Division.

"When law enforcement officers abuse their authority, they not only violate the law but they also threaten the ability of responsible officers to earn the public trust and do their jobs effectively," Principal Deputy Assistant Attorney General Vanita Gupta said in the statement. 

A former prosecutor was sentenced on Thursday in a separate case related to the same incident. The ex-prosecutor, Bliss Worrell, received a sentence of 18 months' probation for concealing knowledge of a felony. She admitted to knowing about the assault and bringing charges against M.W. anyway. One of the charges against M.W. was an attempted escape allegation that was false and meant as a cover-up to explain his injuries, the federal prosecutors said.

(Reporting by Fiona Ortiz; Editing by David Gregorio)