Colorado became the 22nd US state to abolish the death penalty on Monday, after Governor Jared Polis signed a repeal bill into law.

Polis also commuted the sentences of all three men on Colorado's death row to life without possibility of parole.

Colorado’s Democrat-controlled Legislature passed repeal legislation this year after picking up the support of some Republican lawmakers. The vote wasn’t strictly along party lines; some Democrats opposed the initiative on personal or religious grounds.

Colorado has rarely used the death penalty in recent decades. Its last execution was in 1997, and the one before that in 1967. But eliminating it proved tough for repeal supporters: Since 2009, it took six legislative efforts before the 2020 legislation was passed.

The law applies to offences charged starting 1 July.

Polis had previously suggested he would consider clemency for the three men on Colorado's death row. The three cases played a prominent role in the death penalty debate over the years.

Nathan Dunlap was sentenced to die for the shooting deaths of four young employees of a Chuck E Cheese restaurant in Aurora in 1993. Then-governor John Hickenlooper, now a Democratic candidate for a US Senate seat, delayed indefinitely Dunlap’s execution in 2013.

Robert Ray and Sir Mario Owens were on death row for the 2005 ambush slayings of Javad Marshall-Fields and his fiancee, Vivian Wolfe. Marshall-Fields and Wolfe were slain to prevent them from testifying in a separate murder case against Owens.

Marshall-Fields’ mother, Democratic state Senator Rhonda Fields, passionately defended the death penalty each time lawmakers debated repeal.

In a statement, Polis said that “the commutations of these despicable and guilty individuals are consistent with the abolition of the death penalty in the State of Colorado, and consistent with the recognition that the death penalty cannot be, and never has been, administered equitably in the State of Colorado.”

Opponents insisted that the death penalty compelled countless defendants to seek plea deals to solve or close cases. They also said it should be up to voters to decide whether to repeal.

In Colorado's last execution in 1997, Gary Lee Davis was put to death by lethal injection for the 1986 kidnapping, rape and murder of a neighbour, Virginia May.

New Hampshire was the last state to repeal the death penalty in 2019. Several Western states also have moved to abolish capital punishment or put it on hold.

Wyoming’s Legislature came close last year, and another initiative there this year had 26 Republican sponsors. Washington state lawmakers are trying to remove the death penalty from state law. In 2019, New Mexico’s Supreme Court set aside the death penalty for the final two inmates awaiting execution after the state's 2009 repeal.