"America's criminal justice system is badly in need of reform. For too long, our justice system has reinforced our country's cruel history of racism and economic inequality," O'Malley, the former Maryland governor, wrote in a detailed policy paper.
If elected, O'Malley also vowed to restore felons' voting rights and downgrade marijuana's Drug Enforcement Agency schedule, which currently classifies the drug among such substances as heroin and ecstasy.
"All those who served time and re-entered society should be allowed to vote," according to the white paper. "O'Malley will call for and strongly support legislation restoring voting rights to individuals with felony record."
On marijuana, the white paper said O'Malley would "direct the attorney general to move to reclassify marijuana, while supporting bipartisan congressional efforts to legislatively reclassify marijuana as a Schedule II drug."
O'Malley abolished the death penalty in 2013 in Maryland while he served as governor. His white paper called the death penalty a "racially biased and ineffective deterrent."
"As president, he will continue to oppose capital punishment and work to abolish death sentences under federal laws," the paper reads.
O'Malley's proposals are timely. Liberal activists, particularly those associated with the "Black Lives Matter" movement, are hungry for action on criminal justice reform. The past year has seen an uptick in racial tension, spurred by a handful of high-profile cases involving while law enforcement officers killing black men and women.
O'Malley apologized earlier this month for saying "All lives matter" while discussing police violence against African-Americans with liberal demonstrators at the Netroots Nation conference in Phoenix. Several demonstrators interrupted his speech at the event, to the point that O'Malley had to leave the stage.
Since then, however, the governor has tried to correct his statement on "Black lives matter." He told organizers at Netroots Nation that he would release a plan on criminal justice -- which he did Friday -- and spoke at the National Urban League in Fort Lauderdale earlier in the day.
"Every year we bury 300 young black men who died violent deaths on our streets. And black lives matter," he said at the event.
At the same speech, the governor said, "Lots of people can talk about criminal justice reform. I have actually done it."
O'Malley's aides have made a point in framing the governor as the candidate of big ideas. He has released a number of policy papers, including on climate change, and regularly touts his policy focus.
The tactic, however, has not worked yet. Most national polls show the governor lagging far behind former Secretary of State Hillary Clinton -- who herself has focused considerable time on criminal justice reform -- and Vermont Sen. Bernie Sanders.