CHICAGO (Reuters) - Chicago Police on Wednesday finalized stricter limits on when officers can use firearms and other force, the latest attempt to reform a department roiled by misconduct and criticism in the wake of a high-profile 2014 shooting of a black teen by a white officer.

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Police Superintendent Eddie Johnson said the use-of-force policy changes spell out more clearly when it is considered reasonable and necessary, and include new prohibitions on force that is discriminatory or employed as punishment.

Changes also bar officers from shooting at a fleeing suspect unless the person presents an imminent threat, and require officers to use de-escalation techniques. The definition of deadly force was expanded to include chokeholds and striking a subject’s head with an impact weapon.

Experts said the changes, the first to Chicago’s policies since 2002, marks a shift in thinking about force already adopted in cities such as Seattle and Baltimore.

“This policy at the end of the day will save lives and the careers of officers,” said Chuck Wexler, executive director of the Washington, D.C.-based Police Executive Research Forum.

Finalized after months of discussion and revisions, the new rules - which also affect use of Tasers, chemical spray and canines - will start in autumn, after officer training. Johnson said they are meant to address police safety and civil rights concerns.

“I know there will be some who think these policies are too restrictive for officers to do their jobs, and some will think it will not be restrictive enough,” he told a news conference.

Some advocates for reform called it a victory and said it could help rebuild public trust. But Kevin Graham, president of Chicago’s police union, disputed in a statement that excessive force was a widespread problem or that policies needed updating.

The tightened rules come as Mayor Rahm Emanuel attempts to reform the police department.

The U.S. Department of Justice launched an investigation into Chicago Police Department practices in the wake of the 2014 incident in which black teenager Laquan McDonald was shot to death by a white officer. A video of the shooting, released in 2015, sparked days of protests.

It was one of many high-profile incidents that thrust Chicago and other U.S. cities into a national debate over the use of excessive force by police against minorities.

In January, the federal investigation found that Chicago police routinely violated the civil rights of people and cited excessive force, including cases of officers shooting at fleeing suspects and using Tasers on children. It also found racially discriminatory conduct and a “code of silence” to thwart investigations into police misconduct.

Police said the new rules apply a more restrictive justification for deadly force than required by state law.