WASHINGTON — Renewing his attack on capital punishment, Justice Stephen G. Breyer said in a dissent on Monday that his colleagues were wrong to turn down a challenge to California’s death penalty system, which he called unreliable, arbitrary and plagued by “unconscionably long delays.”

The case was brought by Richard D. Boyer, who has cited the stress of his long wait on death row after being sentenced in 1984 for the murders of an elderly couple in Fullerton, Calif. Referring to the conclusions of a state commission in 2008, Justice Breyer said the delays in Mr. Boyer’s case were the product of a dysfunctional system.

“More California death row inmates had committed suicide than had been executed by the state,” he wrote. “Indeed, only a small, apparently random set of death row inmates had been executed. A vast and growing majority remained incarcerated, like Boyer, on death row under a threat of execution for ever longer periods of time.”