HARTFORD, Conn. — Connecticut’s highest court has struck down the state’s death penalty, sparing the lives of 11 killers on death row in a ruling that adds momentum to a nationwide movement to abolish executions.

A 2012 state law repealed the death penalty for future crimes while preserving it for those already condemned to die, but the court ruled Thursday that the punishment “no longer comports with contemporary standards of decency” and violates the state’s constitution.

The divided, 4-3 ruling cited factors that have come up in other states to abolish the death penalty including racial and economic disparities in its use, the costs involved with appeals, the cruelty of the wait for execution and the risk of executing innocent people.

“They went at this from multiple angles in a way that is going to provide ammunition for abolitionists across the country,” said David McGuire, an attorney with the American Civil Liberties Union of Connecticut.

Opposition to the death penalty has been growing in the United States. Thirty-one states still have capital punishment, but several others have turned against it in recent years, including Nebraska, which voted for abolition in May, and Maryland, which abolished it in 2013. Robert Dunham, executive director of the nonprofit Death Penalty Information Center, noted that the number of death sentences imposed last year marked a 40-year low in the country.