Maryland Gov. Martin O'Malley speaks at a rally in support of repealing the state's death penalty in Annapolis on Jan. 15. (AP Photo/Patrick Semansky)

Maryland Gov. Martin O’Malley (D) pressed lawmakers to abolish the death penalty at a pair of charged hearings on Thursday, invoking morality and fairness while arguing that capital punishment is at odds with “our values as a people.”

Prosecutors and others countered with sometimes graphic detail from some of the state’s most gruesome rapes and murders, saying that executions are a vital law enforcement tool.

“Are we really going to walk away from the death penalty for individuals who commit the most heinous of acts?” Baltimore County State’s Attorney Scott Shellenberger asked, recalling a murderer who taunted his victims’ families during his sentencing hearing.

The legislation, which would replace the death penalty with life in prison without the possibility of parole, is among the most high-profile issues facing the legislature during its 90-day session. With O’Malley’s backing, it has also gained momentum recently in a General Assembly that has balked at previous repeal efforts.

O’Malley also argued Thursday that death penalty prosecutions waste resources that could be spent on other crime-fighting strategies and carry the risk of killing an innocent person.

Vicki Schieber didn’t care about the death penalty before her daughter Shannon was raped and murdered. Now she’s working in her memory to end capital punishment and is on the verge of a breakthrough, thanks to Maryland Governor Martin O’Malley. (The Fold/The Washington Post)

“There is no such thing as a foolproof death penalty,” O’Malley said the outset of a packed, five-hour Senate hearing, before heading to the House of Delegates to make the same case. “And there is no way to reverse our ‘mistake’ if we should execute an innocent person.”

He asked senators if the United States should be in the company of six other nations where the majority of executions occur: Iran, Iraq, China, North Korea, Saudi Arabia and Yemen.

O’Malley had some high-profile allies. The head of the NAACP, Benjamin T. Jealous, Archbishop William E. Lori of Baltimore and Kirk Bloodsworth, a former death-row inmate exonerated by DNA evidence, were among those who also testified in favor of the repeal bill, which would make Maryland the 18th state to abolish the death penalty.

Twenty-five members of the Senate — one more than needed to pass the bill — have announced their support. And there were hints Thursday that the number could grow.

Before the hearings, Senate President Thomas V. Mike Miller Jr. (D-Calvert) — a death penalty supporter — predicted to reporters that a bill will pass his chamber “with a comfortable margin.”

A vote could come by the end of the month.

Repeal advocates say they also are optimistic about securing enough votes in the House, which has long been viewed as the chamber more friendly to their efforts.

In recent years, the bill has died in the Senate Judicial Proceedings Committee, where O’Malley was the lead-off witness on Thursday.

But this session, Miller has pledged to allow the bill to be considered by the full chamber if O’Malley can demonstrate that he has enough votes.

Miller and others have predicted that, if passed, the bill will probably be petitioned to referendum, meaning state voters would have the final say in November 2014.

Under the Maryland Constitution, citizens may petition laws to the ballot if they collect enough signatures.

O’Malley was quizzed in both hearings about whether he would commute the sentences of the five inmates on death row in Maryland if the repeal bill passes.

The bill would not directly affect their cases. O’Malley was noncommittal, saying he would “decide each of those cases as they ripen.”

The governor was also pressed about how the state should punish inmates already serving life sentences who kill fellow prisoners or prison personnel.

In response to a question by Sen. Joseph M. Getty (R-Carroll) about “natural-born killers,” O’Malley said his corrections secretary was working on strategies to better manage that element of the prison population.

Percel O. Alston Jr., the legislative chairman of the Maryland Fraternal Order of Police, later testified that rank-and-file prison guards and law enforcement officers consider the death penalty “a layer of protection” and urged lawmakers to keep it on the books.

Mary Lou McDonough, the warden at the Prince George’s County Department of Corrections, offered a different take, saying “good management keeps jails and prisons safe.” She supports the repeal bill.

Lt. Gov. Anthony G. Brown (D), who is ramping up to run for governor next year, also endorsed O’Malley’s bill, pointing to statistics showing that African Americans make up 13 percent of the U.S. population but 41 percent of those on death row.

“There are biases in the system that we will never eliminate in our lifetime,” Brown said.

O’Malley last sponsored a repeal bill in 2009. The Senate balked, instead passing an amended bill that tightened evidentiary standards in capital cases.

Miller said Thursday that he would like the legislature to pass a second bill this year that would broaden those standards. The bill would take effect if a repeal law is rejected by voters.

Kate Havard and Paul Schwartzman contributed to this report.