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A 2012 state law repealed the death penalty for future crimes while preserving it for those already condemned to die.

However, the court ruled 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.