The highest-ranking Baltimore officer charged in the death of Freddie Gray was acquitted on Monday, dealing yet another blow to those who hoped the Gray case would be at the forefront of national police reform.

Lt Brian Rice was found not guilty of involuntary manslaughter, reckless endangerment and misconduct. Rice’s is the fourth trial in which prosecutors have failed to win a conviction. Two prior cases ended in an acquittal, and a third in a hung jury.

Gray, a 25-year-old African American, died last year of injuries sustained while in police detention, prompting weeks of unrest in Baltimore.

Rice first initiated the chase against Gray on the morning of 12 April 2015, although he was not present when Gray was arrested. Rice ordered that Gray’s legs be shackled in the police van where he sustained a fatal spine injury. According to prosecutors the decision not to seatbelt Gray after placing him in the van set the stage for Gray’s death. Inmates who are shackled and transported, without a seatbelt, can be jostled violently, particularly when officers intentionally take sharp turns in what Baltimoreans call a “rough ride”.

“Lt Rice’s decisions on 12 April cannot be blamed on poor judgment or error. His decisions form a chain and that chain led to the death of Freddie Gray,” prosecutor Janice Bledsoe said in closing arguments. “If he had broken that chain and taken one small step of compassion and humanity, Freddie Gray would still be alive.”

But Judge Barry Williams said Rice’s action fell short of criminal. “The state failed to show that the defendant, even if he was aware of the risk, consciously disregarded that risk,” he said.

Williams also said prosecutors failed to show that Rice was aware of a newer policy that required officers to protect prisoners with seatbelts.

Two of the lesser charges had already been dropped – one by the judge and one by prosecutors themselves at the beginning of the trial.

The verdict was no surprise to observers, since most of the witnesses and evidence were the same as those in the previous trials, two of which ended in acquittals, and the third with a hung jury. Williams presided over both of those acquittals, during which he heard similar evidence.

Prosecutors have already lost what was believed to be the state’s strongest case, against officer Caesar Goodson, the driver of the van in which Gray sustained his injuries. Some observers have wondered why the prosecution has decided to continue pursuing charges against the officers. The local Fraternal Order of Police has publicly called on top prosecutor Marilyn Mosby, who is African American and one of the youngest chief prosecutors in the country, to drop the remaining charges.

“I’m disgusted, as usual, and they’re sending a daily message all across the world that our lives don’t matter, and that’s sad,” Tawanda Jones said outside the courthouse. “We’re more than hashtags and body bags.”

Jones was there to mark the third anniversary of her brother, Tyrone West, who died after an altercation with police. Mosby has declined to reopen his case and press charges against any of the officers involved.

Despite the failure to bring any convictions, the Gray cases have highlighted discussions of the role of police in impoverished communities like the Sandtown-Winchester neighborhood where Gray was arrested and the police department just released new use of force guidelines that encourage de-escalation strategies associated with community policing.

“You’re going to have to decide what is reasonable,” chief deputy state’s attorney Michael Schatzow said in closing arguments, setting forth what’s at stake in the trials as the country reacts to a new wave of highly publicized cases where police have killed African American men. “What should the police do?”

But Judge Williams, who previously worked in the civil rights division of the Department of Justice, could not rule on the role of policing in the city, which is still experiencing a homicide crisis, and limited his decision to the elements of the crimes that Rice was charged with.

In a statement, Mayor Stephanie Rawlings-Blake said: “This has been a very difficult time for our city and I thank the community for their patience during this time and ask their continued respect for the judicial process as we move forward.”

She added that Rice will now face an administrative review by the police department.

The next trial, of officer Garrett Miller, is scheduled to begin later this month.

The Associated Press contributed reporting