Given this dire set of facts, the city’s top prosecutor announced on Tuesday that she would no longer bother with marijuana cases, a controversial move that she argued would improve police-community relations and allow law enforcement to devote more time to serious violent crime.
“If you ask that mom whose son was killed where she would rather us spend our time and our attention — on solving that murder, or prosecuting marijuana laws — it’s a no-brainer,” said Marilyn Mosby, the state’s attorney for Baltimore. She vowed at a news conference to no longer prosecute marijuana possession, regardless of quantity or prior criminal record, and said she would seek to vacate almost 5,000 convictions.
Ms. Mosby’s move places her in a vanguard of big-city prosecutors, including Kim Foxx in Chicago, Larry Krasner in Philadelphia, Cyrus R. Vance Jr. in Manhattan and Eric Gonzalez in Brooklyn, who are moving away from marijuana cases, declaring them largely off limits and in some cases going so far as to clear old warrants or convictions off the books.
Much of their reasoning sounds familiar from the many statewide campaigns that have resulted in outright legalization: Marijuana, they say, is not linked to violent crime. Enforcing its prohibition is a waste of resources, and has left thousands of people with criminal convictions that hinder their search for jobs and housing.
But increasingly, another argument is creeping in: Letting marijuana cases go actually makes communities safer, by shifting the focus to stopping violence and untangling a legacy of racial discrimination, allowing the seeds of trust to germinate in neighborhoods where a chief complaint of police officers is that no one will help them solve crimes.
The Baltimore police do not share her view, however, and the response to her announcement immediately cast doubt on how effective it would be. The mayor, Catherine E. Pugh, applauded Ms. Mosby’s attempt to address the “unnecessary criminalization” of marijuana users, but stopped short of endorsing the new policy.
The interim police commissioner, Gary Tuggle, said he would not tell officers to stop making marijuana arrests.
“Without the police, this is just political theater,” said Thiru Vignarajah, a former Maryland deputy attorney general who ran against Ms. Mosby in the 2018 Democratic primary. Mr. Vignarajah noted that many of those who are found with marijuana these days are issued citations and allowed to go on their way anyway.
More than 90 percent of marijuana citations between 2015 and 2017 were issued to black residents, who make up roughly two-thirds of the population.
Other critics of the prosecutor’s move called the announcement too little, too late. Tre’ Murphy, a community activist with Black Leaders Organizing for Change, initially expressed support. “Wow, it’s a major overhaul,” he said. But a few beats later, his skepticism set in, and he wondered why it had not happened until Ms. Mosby’s second term in office.
“I don’t think we can afford to wait these long time frames,” he said. “Until we recognize the harm that many of these policies have caused and rebuild these institutions from the ground up, people will never trust it.”
Ms. Mosby’s first term was occupied by a series of epic police scandals, which placed her at odds with the department. Other prosecutors across the country have moved more quickly on the issue.
In Chicago, Ms. Foxx said her office will move to expunge all misdemeanor marijuana convictions. In St. Louis County, Wesley Bell will prosecute no marijuana cases involving amounts under 100 grams. In Boston, Rachael Rollins has pledged to stop prosecuting drug possession and possession with intent to distribute, along with 13 other crimes.
Advocates for decriminalization applauded Ms. Mosby’s new rules for pushing the envelope. People will not be prosecuted for marijuana possession at all, and will not be charged with distribution or intent to distribute based on quantity alone — there must also be other indicators of drug dealing, such as scales or plastic bags.
Ms. Mosby said people charged with felony distribution for the first time will automatically be referred to a diversion program designed to help them enter the job market. Successful completion of the two-year program can result in expungement of the case.
The new policy would not apply in cases where a defendant faces multiple charges, such as possession of both marijuana and a gun, Ms. Mosby said.
Ms. Mosby said her office would also seek to pass a statute that would make it less cumbersome for prosecutors to overturn a conviction marijuana possession when the circumstances warrant.
Police departments and unions have sometimes put up resistance to these broad uses of prosecutor discretion, saying they defy the intent of lawmakers. Ms. Mosby said that when she briefed Commissioner Tuggle, “He said he felt that marijuana drives violent crime, and I explained to him that is not the case.”
After her announcement, the interim commissioner released a statement confirming that arrests will continue “unless and until the state legislature changes the applicable laws (on marijuana possession ).”
A new police commissioner, Michael Harrison of the New Orleans Police Department, will arrive next month — the fifth person to head the department since Ms. Mosby took office.
In 2016, Mr. Harrison publicly embraced a legal change that allowed the New Orleans police to handle most marijuana possession cases by issuing a summons, and said that officers would have to get permission to make arrests in those cases.
In Baltimore, the police have few grounds to claim that the status quo is working well.
First there was the shocking case of the elite Gun Trace Task Force, whose members robbed residents and planted evidence. Then there were the bodycam videos that appeared to show officers staging the discovery of evidence. A recent investigation by Buzzfeed and TheTrace.org examined the department’s failure to solve, or in some cases even investigate, shootings.
The department’s credibility is so tattered that in April, when the police commissioner himself testified that he had found a loaded gun in a driver’s glove compartment, the jury acquitted the man.
A settlement with the Justice Department to correct systemic racial disparities and excessive use of force has proved to be a challenge. Last week, the judge overseeing the settlement said the department seemed to have a “culture of timidity” when it came to confronting corruption.
Ms. Mosby has been called a divisive figure, particularly after her handling of the case of Freddie Gray, whose death from injuries sustained in police custody set off weeks of unrest. Ms. Mosby charged six officers in the death, and then — after a hung jury and three acquittals — dropped the prosecution, dishing out blame for what she called the Police Department’s failure to conduct an unbiased investigation. She was attacked for being too progressive and for not being progressive enough.
But last year, it became clear that Ms. Mosby understood her base: communities in the city that were both overpoliced for minor infractions and underprotected from violence, with serious crimes going unsolved in their neighborhoods.
In the 2018 primary, she defeated Mr. Vignarajah and another opponent, Ivan Bates, by wide margins, and was unopposed in the general election.