California’s governor has signed a moratorium halting the use of the death penalty, saying he would be unable to sleep at night if he sent just one innocent person to their death.

Gavin Newsom, who was sworn in as the state’s 40th governor in January, said statistics suggested at least one of the 737 inmates on California’s death row – more than any other state – ought not to be there.

Citing a National Academy of Sciences report that estimated 1 out of every 25 people on death row was innocent, the governor said he was not prepared to go along with such a system.

“If that’s the case, that means if we move forward executing 737 people in California, we will have executed roughly 30 people that are innocent,” Mr Newsom told reporters in the state capital, Sacramento. “I don’t know about you. I can’t sign my name to that. I can’t be party to that. I won’t be able to sleep at night.”

The use of the death penalty remains a highly emotional issue across the country, and the governor has his critics.

Death row in California's San Quentin prison Show all 8 1 /8 Death row in California's San Quentin prison Death row in California's San Quentin prison A condemned inmate exercises in a cage out in the yard of San Quentin prison Getty Death row in California's San Quentin prison San Quentin State Prison opened in 1852 and is California's oldest penitentiary. The facility houses the state's only death row for men that currently has 700 condemned inmates Getty Death row in California's San Quentin prison The lethal injection facility at San Quentin prison AP Death row in California's San Quentin prison A condemned inmate stands in a cell out in the yard of San Quentin prison Getty Death row in California's San Quentin prison An armrest in the interior of the lethal injection facility at San Quentin prison AP Death row in California's San Quentin prison A cell on death row in San Quentin Getty Death row in California's San Quentin prison A cage on death row in San Quentin Getty Death row in California's San Quentin prison A cell on death row in San Quentin Getty

Michelle Hanisee, president of the Association of Deputy District Attorneys, a prosecutors’ association, claimed voters of the state supported the death penalty,

“Governor Newsom, who supported the failed initiative to end the death penalty in 2006, is usurping the express will of California voters and substituting his personal preferences via this hasty and ill-considered moratorium on the death penalty,” she said.

Others praised the move and said studies had shown people of colour had long been discriminated against when it came to the application of the death penalty and capital sentencing.

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Shari Silberstein, executive director of Equal Justice USA, a New York-based campaign group, said Mr Newsom had “written a new chapter in the history of justice reform”.

“This is a sweeping move that reflects just how deeply the death penalty has failed. My hope is this will also lead Americans to reconsider our nation’s approach to violence overall,” she said. “Our overly punitive approach has devastated communities of colour, deepened racial disparities, and traumatised millions of families.”

Experts say support for executions in California has fallen considerably in recent decades. However, in both 2012 and 2016, voters there rejected ballot measures that were intended to abolish the death penalty

Mr Newsom said the equipment in the execution chamber at San Quentin state prison was already being dismantled, and that he was withdrawing California’s lethal injection protocol.

The order will not alter any current conviction or sentence, or lead to the release of any prisoner currently on death row, he said.

California has not put an inmate to death since 2006, amid legal challenges to its execution protocols.

The move was criticised by Donald Trump.