SACRAMENTO — Major law enforcement organizations dropped their opposition Thursday to California legislation that strengthens standards for when officers can use deadly force, a shift that followed changes to the measure.

The measure would bar police from using lethal force unless it is “necessary” to defend against an imminent threat of death or serious bodily injury to officers or bystanders. It was prompted by public outrage over fatal police shootings, including the killing of unarmed vandalism suspect Stephon Clark in Sacramento last year.

The current standard lets officers kill if they have “reasonable” fear they or others are in imminent danger, a threshold that makes it rare for officers to be charged following a shooting and rarer still for them to be convicted.

“With so many unnecessary deaths, I think everyone agrees that we need to change how deadly force is used in California,” said Democratic Assemblywoman Shirley Weber of San Diego, who wrote the measure. “We can now move a policy forward that will save lives and change the culture of policing in California.”

The issue has spawned emotional testimony from those who have lost loved ones in confrontations with police and from officers who have been involved in shootings on the job.

Law enforcement officials did not explain their decision. But a revised version of the bill filed Thursday drops an explicit definition of “necessary” that was in the original. The deleted language said officers could open fire when there is “no reasonable alternative.”

Measure Makes Clear That Officers Are Not Required to Retreat or Back Down

The amended measure also makes clear that officers are not required to retreat or back down in the face of a suspect’s resistance and officers don’t lose their right to self-defense if they use “objectively reasonable force.”

Amendments also strip out a specific requirement that officers try to de-escalate confrontations before using deadly force but allow the courts to consider officers’ actions leading up to fatal shootings, said Peter Bibring, police practices director for the American Civil Liberties Union of California, which proposed the bill and negotiated the changes.

“The courts can still consider whether officers needlessly escalated a situation or failed to use de-escalation tactics that could have avoided a shooting,” he said.

The ACLU considers the revised measure to still have the strongest language of any in the U.S., though legal experts split on the significance of Thursday’s changes.

“This is so watered down,” said Ed Obayashi, a use-of-force consultant to law enforcement agencies and a Plumas County deputy sheriff. “The language is virtually legally synonymous with current constitutional standards for use of force. It really is a distinction without a legal difference.”

But University of South Carolina law professor and former Tallahassee, Florida, police officer Seth Stoughton called it a significant change to current state law.

The revised bill “does a better job than any law that I’m aware of in defining what is an imminent threat,” he said.

Law Enforcement Opponents Blocked Passage of a Similar Measure

“It doesn’t do everything the original bill had in it, but it brings California from the lowest tier in the country in to the highest tier in the country and you’re left with a feasible, reasonable standard that I think is going to go a long way to protecting officers and community members,” Stoughton said.

Democratic Gov. Gavin Newsom and Democratic leaders in the Legislature backed the revised version, which is set for an Assembly vote next week. Newsom called it “an important bill, one that will help restore community trust in our criminal justice system.”

Law enforcement opponents blocked passage of a similar measure introduced last year after police killed Clark, an unarmed black man. The death set off intense protests.

The Peace Officers Research Association of California, which represents rank-and-file officers, and the California Police Chiefs Association both removed their opposition and moved to neutral positions. The groups were the key law enforcement negotiators with Weber’s office and the ACLU.

Six other associations representing state, county and local law enforcement officers and the California Statewide Law Enforcement Association all also withdrew their opposition.

Law enforcement organizations are backing a related Senate measure that would require that every officer be trained in ways to avoid opening fire.