The Maryland General Assembly on Friday approved a measure to ban capital punishment, which would make the state the 18th in the U.S. to do so. It now needs the governor's approval.

Gov. Martin O'Malley is expected to sign it.

Supporters argue that capital punishment is costly, error-prone, racially biased and a poor deterrent. Opponents say it's a necessary tool to punish those who commit the most egregious crimes.

Maryland has five men on death row, though the measure makes it clear the governor can commute their sentences to life in prison. The state's last execution took place in 2005.

Capital punishment has been on hold in Maryland since a December 2006 ruling by the state's highest court that the lethal injection protocols weren't properly approved by a legislative committee.

Maryland has a large Catholic population, and the church opposes the death penalty.

According to the Maryland Department of Public Safety & Correctional Services website, Maryland has only executed five inmates since 1976.

In contrast, neighboring Virginia has executed 110 inmates since the U.S. Supreme Court restored capital punishment in 1976, according to the Death Penalty Information Center. However, Virginia's death row population has dwindled to eight from a peak of 57 in 1995, in part because fewer death sentences are being handed down in the state amid an increased acceptance of life without parole as a reasonable alternative.

The center said death sentences have declined by 75 percent and executions by 60 percent nationally since the 1990s.