Last month, Sacramento police fired 20 rounds at Stephon Clark in his grandmother’s backyard, fatally striking the unarmed, black 22-year-old eight times.

According to the officers, they mistook the cellphone in Clark’s hand for a gun and fired after they said he advanced toward them with the item outstretched. The body camera video does not confirm or deny whether Clark advanced on them because Clark's body is not visible until he is shown laying on the ground.

The young man’s death has sparked protests in Sacramento, as well as nationwide accusations of racist and overzealous policing. The county District Attorney, with oversight from the state, is investigating the matter.

In most cases where police are responsible for the death of citizens, which disproportionately involve black men, officers are either cleared of criminal charges or not charged at all.

In California, though, cops in similar situations could soon find themselves subject to a new legal standard -- the strictest in the country. If passed, it could provide a model for other progressive states that have followed California's lead on other issues, including immigration and the environment.

In 1989, the Supreme Court set the minimum standard for police using deadly force as one of “objective reasonableness” -- that is, the officer’s actions must be reasonable to an objective observer, taking into account only what the officer knew at the time he or she decided to use force. Within this framework, any reasonably perceived threat to the officer or the public justifies the use of deadly force.

But after Clark’s death, California Assemblymembers Shirley Weber and Kevin McCarty introduced legislation that would change the legal standard for lethal force in their state to only be used “when necessary" and after every other nonlethal option has been exhausted.

“The bill says lethal force should only be used when it’s necessary, and that necessity is only when the public or an officer is in imminent danger. If an officer [or member of the public] is not about to be hurt, officers should use other [de-escalation] strategies,” such as verbal warnings, tasers and pepper spray, says Weber.

The bill would also require investigations to assess whether officers created a situation resulting in the necessity to use lethal force.

“Under current law, if an officer jumps in front of a moving vehicle, they can legally kill the driver because now they’re suddenly in harm’s way,” Lizzie Buchen of the American Civil Liberties Union told the New Republic. “What this law would say is that that officer needs to be held accountable for creating the necessity of killing the driver.”

Two other states -- Delaware and Tennessee -- have laws on the books requiring officers to exhaust all other options before resorting to deadly force. Broadly, though, states use the Supreme Court's "objective reasonableness standard" when assessing officers’ actions in the field.

According to Joanna Schwartz, a professor of law at UCLA, the ideas behind the legislation are not new -- they're just not yet reflected in the law. Many police departments across the country require officers to use de-escalation techniques. Campaign Zero, the policy arm of Black Lives Matter, assessed large police departments with these kinds of policies and found that stronger de-escalation policies led to fewer police killings.

Although the California law would be the strictest statewide legislation of its kind, it doesn't mention criminal penalties. The decision about whether to prosecute would still be at the discretion of prosecutors, says Weber.

Because of that, legal experts say it wouldn't necessarily result in jailtime for police found in violation of the standard.

“There’s no reason this standard would have anything to do with what counts as a crime. Some courts have imported constitutional standards about use-of-force into criminal law, but the two don’t necessarily belong together,” says Brandon Garrett, a professor at the University of Virginia School of Law who has researched the benefits of reducing police discretion.

But some think the new standard would make it easier to prosecute police anyway -- or at least instill fear among officers.

“This is a giant invitation to prosecute law officers where they have not been prosecuted before,” says Eugene O’Donnell, a professor at John Jay College of Criminal Justice and a former NYPD officer. “I don’t understand the reason or the point to engage in this kind of lawmaking if it’s not to threaten officers that if they make a mistake they could end up being criminally prosecuted.”

To be clear, O’Donnell believes the standards and strategies outlined in the bill are widely beneficial to policing -- but he believes they should be adopted by departments as policies, not legislated by politicians.

Law enforcement organizations have come out in strong opposition to the legislation. The California Police Chiefs Association last week held a meeting to denounce it. David Swing, president of the association, told the Mercury News that “evaluating the use of deadly force from the perspective of hindsight and narrowing the justifiable homicide defense will lead to officers pulling back on proactive policing, resulting in increased crime throughout the state.”

Stephon Clark's family, as well as advocacy organizations like Black Lives Matter and the ACLU, support the bill.

It has a decent chance of passage, given that Democrats control the state's assembly, senate and governor's office.