Mr. Khalifa, now 29 and serving a sentence of 25 years to life, is one of hundreds of people convicted in California under a legal doctrine known as the felony murder rule, which holds that anyone involved in certain kinds of serious felonies that result in death is as liable as the actual killer.

“I knew I didn’t kill anyone,” Mr. Khalifa said. “I felt and kind of knew that I was going to spend the rest of my life in prison. It didn’t seem like there was any room to be a human being again. My life was over.”

But the hard doctrine that sent Mr. Khalifa to prison may be softening. A bill moving through the California Legislature would change state law so that only someone who actually killed, intended to kill or acted as a major player with “reckless indifference to human life” could face murder charges.