Patrick Semansky / AP Maryland Gov. Martin O'Malley, center, speaks at a rally in support of repealing the state's death penalty in Annapolis, Md., on Jan. 15. O'Malley argued that the death penalty is a waste of resources that could be better used to fight crime in more productive ways.

Maryland will become the 18th state to ban the death penalty.

A bill to outlaw capital punishment cleared the state House of Delegates on Friday and has already been approved by the Senate. Gov. Martin O’Malley, a Democrat, has said that he will sign it.

O’Malley told reporters after the vote that the ban validates a “core belief that we share in the dignity of every human being.”

“Overwhelming evidence tells us that the death penalty does not work,” he said earlier in the day on Twitter. He added: “Especially in tough times, if a public policy is expensive and does not work, then we should stop doing it.”

The vote in the House was 82-56.

Maryland has five men on death row; the new legislation would allow the governor to commute their sentences. The state last executed someone in 2005. It has put five people to death since reinstating the death penalty in 1978.

The House of Delegates rejected more than 20 proposed amendments to the ban, most proposed by Republicans, including some that would have allowed the death penalty in certain cases, such as child murders and the killing of police officers.

The other 17 states that have outlawed the death penalty are mostly in the Midwest and Northeast. The District of Columbia has also banned it. Maryland is the sixth state in six years to enact such a ban, according to the Death Penalty Information Center.

O’Malley has been mentioned as a possible Democratic presidential candidate in 2016.

The Associated Press contributed to this report.