“But,” he added, “that’s a heck of a lot easier said than done.”

California voters affirmed the death penalty by a narrow margin in 2012, with 48 percent of voters favoring replacing it with life in prison without parole. That vote, Professor Berman said, “may reflect that they’re comfortable with a system that doesn’t get around to executing somebody.”

The death penalty has been effectively under a moratorium in the state since 2006, when Judge Jeremy Fogel of United States District Court in San Jose ordered changes in the state’s execution methods. In 2008, Ronald M. George, then the chief justice of California, called the system for handling appeals in capital cases “dysfunctional.” A state-appointed commission reached a similar conclusion that year, stating the system was “plagued with excessive delay” in appointing lawyers and in reviews of appeals and petitions before the State Supreme Court.

Mr. Jones’s lead lawyer, Michael Laurence, said in a statement that the legal team was grateful for the decision, adding, “The execution of Mr. Jones, and the others like him whose meritorious legal claims have gone unheard for decades, serves no valid state interest.”

Mr. Jones’s trial for the killing in 1992 of Julia Miller, an accountant, got little attention at the time. It took place down the hall from the murder trial of O. J. Simpson, and The Los Angeles Times published an article comparing the “mundane murder trial” with the nearby “trial of the century.”

Eric M. Freedman, a professor at the Hofstra University law school, said that he doubted the case would make it to the Supreme Court or set national policy on the death penalty, but that it would still resonate.

“The decision is incredibly important in bringing to public consciousness that this has been a political shell game,” he said, with politicians endorsing the death penalty but unwilling to provide the funds for defense lawyers and efficient courts that would keep the system working.

Judge Carney was scathing in his description of California’s administration of capital punishment and said the flaws stemmed mainly from state deficiencies, not abuse of the system by prisoners.