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TRENTON — The debate in the New Jersey Legislature over whether to legalize recreational marijuana is unexpectedly turning into a wrenching discussion about fairness in the criminal justice system and the role of race in hundreds of thousands of drug convictions over the decades.

As lawmakers edge closer to approving a marijuana legalization bill, they are also weighing a groundbreaking companion measure that would clear the criminal records of many people with drug offenses. Ten other states and Washington have decriminalized recreational marijuana, but none has gone so far in addressing historic inequities in drug sentencing in tandem with legalization measures.

Supporters of the proposal in New Jersey to expunge criminal records say strict drug laws in the state have long unfairly targeted minorities: A black New Jersey resident is three times more likely to be arrested on marijuana-related offenses than a white resident, a recent study found.

As Trenton begins to debate a marijuana bill approved on Monday by a joint legislative committee, creating an efficient process for tossing out past convictions has become central to gaining support from lawmakers who represent predominantly African-American communities.