WASHINGTON — Continuing his sustained critique of the American capital justice system, Justice Stephen G. Breyer on Monday issued an unusual dissent from the Supreme Court’s decision not to hear the case of a Florida death row inmate who said his conviction had been based on flawed evidence and false testimony.

Justice Breyer did not discuss the evidence against the inmate, Henry P. Sireci. Instead, he again urged his colleagues to reconsider the use of the death penalty, which he said was unreliable, arbitrary and shot through with racism. In the process, he addressed two other recent death penalty cases, from Ohio and Alabama, in which he said the court had also gone astray.

In Mr. Sireci’s case, Justice Breyer returned to a longstanding concern, saying the court should have considered whether the inmate’s four decades on death row violated the Eighth Amendment’s ban on cruel and unusual punishment.

“He has lived in prison under threat of execution for 40 years,” Justice Breyer wrote of Mr. Sireci. “When he was first sentenced to death, the Berlin Wall stood firmly in place. Saigon had just fallen. Few Americans knew of the personal computer or the internet. And over half of all Americans now alive had not yet been born.”