CHICAGO (AP) — Chicago's police chief on Friday released details of a proposed new policy that would require officers to use the least amount of force necessary and emphasizes the "sanctity of life."

The proposal requires officers to intervene if they see another officer violating department policy. Deadly force could only be used to prevent immediate threat of death or great bodily harm. The announcement comes as the U.S. Department of Justice investigates the department after a white officer was charged with murder for the fatal shooting of a black teenager in 2014. Laquan McDonald was shot 16 times.

Police Superintendent Eddie Johnson told reporters at a news conference that the draft aims to "clarify response options to officers during split-second decisions or in the critical time before those moments while placing a heavy emphasis on the sanctity of life."

The policy will undergo 45 days of public comment , something the superintendent called a department first and a step toward previously promised transparency efforts. He said the department would use less-lethal methods as often as possible.

"When I say to you that this is a new day at CPD, it's not a joke and I'm not kidding about it," Johnson said.

After the public feedback period ends Nov. 21, the department will review contributions with the goal of having a final version of the policy by the end of the year. Officers will then be trained according to the policy.

Anne Kirkpatrick, the department's chief of organizational development, said the policy includes the need for independent justification every time a tool, like a stun gun or baton, is used in force.

"This is a new way for us to do business," she said.

The policy also would require police to offer medical aid to those injured in use-of-force incidents. It asks them to de-escalate situations and not use force unless "all other reasonable alternatives have been exhausted."

Last month, the department started mandatory de-escalation training to help officers better assess how to respond to complex and tense situations. The department also has expanded its use of body cameras.