On Monday, the first of those officers — William G. Porter, a 26-year-old Baltimore native — will arrive at a downtown courtroom to stand trial.
The proceedings, which will begin with jury selection, could have significant implications for the city and for the five other officers slated to be tried consecutively over the next several months, experts said.
The Baltimore trials have gained national prominence as activists have sought to bring attention to police brutality and to the lack of charges in other cases where young black men have been killed, including Michael Brown in Ferguson, Mo. The rioting that broke out in Baltimore following Gray's death in April from injuries sustained in police custody have heightened interest in the case.
Locally, Porter's trial is expected to be watched closely by residents, public officials and civil rights leaders. The NAACP's local chapter, for example, plans to have a "court watcher" in attendance throughout the trial, which could last weeks.
"We just want fairness and justice for Freddie Gray in a legal, calm way, and the courtroom is where it's happening," said Tessa Hill-Alston, the chapter's president. "We want the prosecutors to do the right thing and continue to press forward and get results."
"This is a different day for Baltimore citizens, to have police go to trial," she said. "This is a monumental thing."
City officers have faced charges in a range of incidents over the years, but critics have been frustrated by a lack of charges in others.
Gray, 25, was arrested in West Baltimore on April 12 and driven around in the back of a police transport van for about 45 minutes before arriving at the Western District police station, where he was found to be unresponsive. He died a week later from a severe spinal cord injury sustained in the van. After rioting broke out on the afternoon of his funeral, Gov. Larry Hogan called in the National Guard and Mayor Stephanie Rawlings-Blake instituted a weeklong nightly curfew.
Mosby charged the six officers on May 1, under a cloud of post-rioting unease that still hung low over Baltimore's streets. The charges were condemned at the time by police union officials as a "rush to judgment." Mosby's office would later credit the decision with restoring order "before the entire city became an armed camp or was burned to the ground."
Porter, who is expected to take the stand, was present at multiple stops of the transport van in which Gray was injured, and prosecutors allege he should have sought medical attention. The Baltimore Sun has previously reported that, according to a police review of Porter's statement to detectives, Porter mentioned not being sure whether Gray was faking his injury. His attorneys have cited another portion of Porter's statement, in which he said he recognized Gray "from the neighborhood," and that it was "always a big scene whenever you attempted to arrest Freddie Gray."
Porter, on the city's force since 2012, is charged with manslaughter, second-degree assault, misconduct in office and reckless endangerment. He has pleaded not guilty, as have the five other officers charged in the case.
William H. "Billy" Murphy Jr., an attorney for Gray's family, did not respond to a request for comment. The city has agreed to pay the family $6.4 million under a civil settlement in the case.
The proceedings Monday will start with the search for a panel of city jurors who can be impartial — forgetting everything they've heard about the highly publicized case and dismissing any emotions about its impact on the city or their own neighborhoods.
Porter's attorneys have said it will be impossible to seat such a panel in Baltimore and that the trial must be moved. Prosecutors have said a fair jury can be seated, and that Baltimore residents deserve the chance to deliver justice in the case.
Judge Barry Williams has said the only way to find out is to call potential city jurors to the court and ask them during the jury selection process, known as voir dire, if they can be fair.
The process could be difficult. During jury selection in the October trial of a young man arrested during the April unrest, 21 potential jurors stood when asked if they had "strong feelings regarding the protest and the ensuing response following the death of Freddie Gray."
The process will yield a jury of 12, with as many as four alternate jurors.
Williams has said he expects to question 75 to 80 potential jurors on Monday.
Neither prosecutors nor Porter's defense attorneys are allowed to discuss the case because of a gag order issued by Williams.
Rawlings-Blake said she is confident Porter can get a fair trial in Baltimore.
"I'm confident. I'm prayerful. I'm hopeful," she said. "This is a very tough time for our city. I trust the judge that has been assigned to this case. He understands what justice is, what fairness is. I know he will uphold the highest standards."
Nonetheless, she said, the city is preparing for protests associated with the trial and around police-involved deaths in Chicago and Minnesota.
"We're having constant conversations and planning sessions," she said. "The police have set up a joint information center. We've set up protocols for surrounding jurisdictions. We're ready."
Rawlings-Blake said police are monitoring social media and talking with community leaders.
"We're vigilant," she said. "Community members certainly don't want the city to erupt in violence again. We're listening."
Hill-Alston said the last thing Baltimore needs is for African-American communities to be destroyed again, or for young black men to be charged criminally for rioting. She said businesses like CVS and Rite-Aid, which are rebuilding after their pharmacies were looted and destroyed in April, have shown good faith in returning and are important resources for elderly residents and others.
Hill-Alston said residents have the right to vent their frustrations through peaceful protesting during and after the trial, but she urged them to remember that Porter's trial does not represent the totality of the state's case in Gray's death.
"There are six trials and I think that we have to take a look at each one, because one may turn out one way and one may turn out another way," she said.
An acquittal in Porter's case would only be the beginning in the state's fight, she said.
"Let's watch the case, and then watch the five others," she said.