The total number of people serving sentences for felony murder in California is unknown because the cases are not tracked separately from other murder convictions. But proponents of the bill estimate that it is between 400 and 800. In 2016, lawmakers rejected a bill that would have required prosecutors to collect data on felony murder prosecutions and report it to the state.

A survey answered by 1,000 prisoners convicted of murder found that the felony murder rule disproportionately affects women and young people. Of the women serving life sentences for murder in California, 72 percent were not the killers, according to the survey, which was conducted by Restore Justice, the Youth Justice Coalition and the Anti-Recidivism Coalition, California groups that support criminal justice reform.

The origins of the felony murder rule are murky. Generations of law students have been taught that it is a relic of British common law.

But Guyora Binder, a professor at the University at Buffalo School of Law and a leading expert on felony murder, said he had found otherwise. He traced modern felony murder doctrine to the 1820s, when state legislatures in the United States codified criminal offenses.

England abolished its version of felony murder in 1957, followed by India, Canada and other common law countries, and the United States remains the only country where the felony murder doctrine still exists. A Michigan Supreme Court ruling that did away with it in that state nearly four decades ago called it “a historic survivor for which there is no logical or practical basis for existence in modern law.”

The proposed California legislation would not undo felony murder entirely, but it would carve out the group of people who had very little involvement in the underlying crime and no intent to kill anyone, Mr. Binder said. That could make it a model for other states.