A bill requiring police to be more careful when applying deadly force against citizens has passed the California legislature and is now heading to the governor's desk.

AB 392, first introduced by California Assemblymember Shirley Weber (D–San Diego), changes how police across the state are expected to evaluate conditions and dangers before resorting to deadly force. Currently, the state requires that police have a "reasonable fear" that they were in danger. Thus, police can argue that the use of deadly force is justified based on what they think might happen, even if it turns out that they were mistaken and there was no actual threat.

Under AB 392, these rules will change. In the text of the bill, a killing by a police officer will be considered justified when:

"the officer reasonably believes, based on the totality of the circumstances, that deadly force is necessary to defend against an imminent threat of death or serious bodily injury to the officer or to another person, or to apprehend a fleeing person for a felony that threatened or resulted in death or serious bodily injury, if the officer reasonably believes that the person will cause death or serious bodily injury to another unless the person is immediately apprehended."

In other words, the police officer has to be able to argue that there is an actual imminent threat in order to justify using deadly force.

The bill was originally introduced in the wake of Stephon Clark's killing by Sacramento Police in March 2018. Police, responding to 911 calls about vehicle break-ins, identified Clark as a suspect, and chased him into a backyard. There, two officers apparently mistook Clark's cellphone for a gun and opened fire on Clark, shooting him eight times and killing him.

The incident was captured on officers' body cameras, but the Sacramento District Attorney's office ultimately decided not to charge the officers, taking the position that the two officers genuinely feared that Clark actually had a gun, and therefore the shooting was justified and the officers "acted lawfully."

Clark's death prompted outrage and calls for reform in the state's rules on police deadly force. AB 392 passed the state's Assembly in May and finally passed the state Senate on Monday by a vote of 34-3.

The bill has been watered down significantly in order to overcome resistance by law enforcement groups. The bill once had an objective definition of what it meant when it called deadly force "necessary" (that a reasonable police officer in the same situation would objectively conclude there was no alternative) that has been removed, leaving it for prosecutors and juries to determine. The bill has been amended to make it clear that officers do not have a duty to retreat when faced with a confrontation, nor do they lose the right to claim self-defense when using reasonable force to arrest somebody or to prevent them from escaping. It does, however, explain that retreating does not mean "tactical repositioning or other de-escalation tactics." In the Clark case, the officers were in a position where they could have safely backed away from him and would have likely realized quickly he did not have a gun.

The bill now heads to the desk of Gov. Gavin Newsom, a Democrat. He praised the bill in May and is expected to sign it into law.

Use of force incidents by police in California is on the decline across the state, and perhaps AB 392 will help. A new report released last week shows a 20 percent drop in instances of use for force from 2016, declining from 782 incidents in a year to 628. In one-third of the 2018 cases, civilians were shot, and 146 were killed.