On Sunday, California significantly restricted the circumstances under which someone can be prosecuted for a murder that they did not commit.

Under the old felony murder rule, people could be charged with murder for a death that occurred during a felony in which they participated, even if they themselves did not kill anyone or even know that someone had been killed. But a law signed by Governor Jerry Brown (Senate Bill 1437) narrows this rule to people who commit murder, intend it, or act with “reckless indifference to human life.”

“Most people have no idea that you could be charged with murder and convicted with murder without having committed murder or even being present when the murder occurred,” state Senator Nancy Skinner, who introduced the legislation, told me.

District attorneys “can no longer threaten everyone with a first-degree life sentence in the same way,” said Kate Chatfield, the policy director of Restore Justice.

The law applies retroactively. People can now petition to have a murder conviction vacated and replaced with a new sentence if they would not have been convicted under this law. Chatfield, who drafted SB 1437, estimates that approximately 800 people could be resentenced in this way.

To benefit from this provision, an incarcerated person would need to file a petition documenting eligibility. If the court establishes a prima facie showing of eligibility, prosecutors who wish to stop a conviction from being vacated would need to demonstrate beyond a reasonable doubt that the individual is ineligible. “We anticipate that a lot of these petitions can be dispensed of rather quickly, that it will often not be contested that somebody was just out of the scene,” Chatfield said. “We learned from the past in order to make the process streamlined from the outset.” The San Francisco public defender’s office said on Monday that it will examine all past homicide convictions to identify individuals in a position to demand a new sentence.

Other bills that Brown signed on Sunday also expand opportunities to modify past sentences. Assembly Bill 2942 will enable prosecutors to reopen cases in order to ask a judge to impose a reduced sentence. For instance, sentences decided under the state’s three-strikes law “could be reduced if prosecutors withdraw a prior conviction … from the court’s consideration,” Kyle Barry reported in The Appeal. This change heightens the stakes of electing DAs committed to acting against excessive sentencing.

AB 1793 shifts the burden of review. It instructs state officials to identify individuals eligible to have marijuana-related convictions expunged or reduced. Although Californians’ ability to petition for such relief grew in 2016, few have taken advantage. “It’s safe to say the number of persons eligible to have their offenses reduced from felonies to misdemeanors is in the hundreds of thousands,” Dale Gieringer, director of California NORML, told the Los Angeles Times.