On Tuesday, the Supreme Court ruled that a Florida law setting a minimum I.Q. test score for the death penalty was too rigid.

Polls have shown a growing dissatisfaction with capital punishment among Americans. If asked for a simple up or down on the death penalty for convicted murderers, 60 percent still back execution, according to a Gallup Poll taken last October. But that support is at its lowest level in more than 40 years.

When pollsters offer the option of life in prison with no chance of parole, supports slips more. In a 2010 Gallup poll, 49 percent said the death penalty was the better punishment for murder, while 46 percent selected life imprisonment with “absolutely no possibility of parole.” A similar question asked a year ago by Quinnipiac University got comparable results.

In a Gallup poll conducted a month before the Supreme Court’s June 2002 ruling barring executions of prisoners with mental disabilities, 82 percent opposed the death penalty for such criminals. It doesn’t appear that any survey organization has asked about capital punishment for the mentally disabled since then.