UPDATE: Judge Alarcon and Prof. Mitchell issued an updated version of their article on the costs of the death penalty in California. Their abstract states:

In a 2011 study, the authors examined the history of California’s death penalty system to inform voters of the reasons for its extraordinary delays. There, they set forth suggestions that could be adopted by the legislature or through the initiative process that would reduce delays in executing death-penalty judgments. The study revealed that, since 1978, California’s current system has cost the state’s taxpayers $4 billion more than a system that has life in prison without the possibility of parole (‘LWOP’) as its most severe penalty. In this article, the authors update voters on the findings presented in their 2011 study. Recent studies reveal that if the current system is maintained, Californians will spend an additional $5 billion to $7 billion over the cost of LWOP to fund the broken system between now and 2050. In that time, roughly 740 more inmates will be added to death row, an additional fourteen executions will be carried out, and more than five hundred death-row inmates will die of old age or other causes before the state executes them. Proposition 34, on the November 2012 ballot, will give voters the opportunity to determine whether they wish to retain the present broken death-penalty system—despite its cost and ineffectiveness—or whether the appropriate punishment for murder with special circumstances should be life in prison without the possibility of parole.

The new article is: Judge Arthur L. Alarcón and Paula M. Mitchell, Costs of Capital Punishment in California: Will Voters Choose Reform this November?, 46 Loy. L.A. L. Rev. S1 (2012). It is available in full text at http://digitalcommons.lmu.edu/llr/vol46/iss0/1.