More states are coming to recognize that the death penalty is arbitrary, racially biased and prone to catastrophic error. Even those that have not abolished capital punishment are no longer carrying it out in practice.

In 2013, Maryland became the sixth state to end capital punishment in the last six years. Eighteen states and the District of Columbia have abolished the penalty, and it is dormant in the federal system and the military. Thirty states have had no executions in the last five years.

As it becomes less frequent, the death penalty also becomes more limited to an extremely small slice of the country, and therefore all the more arbitrary in its application. All 80 death sentences in 2013 came from only about 2 percent of counties in the entire country, and all 39 executions — more than half occurred in Texas and Florida — took place in about 1 percent of all counties, according to a new report by the Death Penalty Information Center. Eighty-five percent of all counties have not had a single execution in more than 45 years.

Public support for the death penalty — an important factor in the Supreme Court’s consideration of its constitutionality — is at its lowest level in four decades, and 40 percent of people surveyed by Gallup say they do not believe it is administered fairly. Surely that is due in part to the hundreds of exonerations based on DNA testing — including 18 death-row inmates — which continue to reveal irreparable failures throughout the system.