A judge on Monday found the highest-ranking officer charged in Freddie Gray’s death not guilty on all counts, dealing a devastating blow to prosecutors, who have now tried four officers without a conviction, and stoking doubts about whether the state can win a guilty verdict against the remaining defendants.

Judge Barry G. Williams acquitted Lt. Brian Rice, 42, of manslaughter, reckless endangerment and misconduct in office after a week-long bench trial, finding that Rice did not commit a crime when he loaded Gray, 25, into a police transport van without seat-belting him. Gray suffered a severe neck injury as he was being taken to a police station and died a week later.

The verdict renews questions about whether prosecutors will go forward or drop charges against the three officers awaiting trial. The judge recently acquitted Officer Caesar Goodson Jr., who drove the transport van, as well as Officer Edward M. Nero, who helped arrest Gray, both after bench trials. Officer William Porter is scheduled to be retried in the fall on manslaughter and other counts after a jury deadlocked in December.

Officer Garrett Miller is facing trial on assault and misconduct charges in late July, and Sgt. Alicia White — who is charged with manslaughter, assault and misconduct — is set to be tried in October.

It is unclear what new evidence or witnesses the state can present to bolster its arguments in the remaining cases. With each passing trial, prosecutors have offered theories about each officer’s culpability in Gray's death, injury or alleged wrongful arrest, but Williams has been incredulous at each turn.

Six Baltimore police officers were charged after Freddie Gray’s death and arrest. Here’s who they are. (Claritza Jimenez,Erin Patrick O'Connor/The Washington Post)

Police arrested Gray in West Baltimore the morning of April 12, 2015, after he ran from officers. Rice and other officers shackled his wrists and legs and put him in the prisoner compartment of a police van without restraining him. Prosecutors say Gray fell and struck his head.

At Porter’s trial, prosecutors said Gray died because the officer callously ignored Gray’s cries for help. At Nero’s trial, the state argued that the officer lacked probable cause to make the arrest and urged the judge to convict him of assault.

For Goodson — who faced second-degree depraved-heart murder, the most serious charge in the case — prosecutors told the judge that the officer gave Gray a “rough ride,” driving recklessly as Gray bounced around inside the police van. Prosecutors laid out the theory in a dramatic opening statement, only to back away from it in closing arguments after the judge challenged their evidence.

In Rice’s case, prosecutors again appeared to modify the theory they presented at the beginning of the trial. In his opening, prosecutor Michael Schatzow argued that Rice should be found guilty because he was the senior officer on the scene of Gray’s arrest; in closing arguments, Schatzow’s counterpart Janice Bledsoe said the lieutenant wanted to “punish and humiliate” Gray for resisting police.

Reading the Rice verdict in a packed courtroom Monday, Williams said Rice’s failure to seat-belt Gray “may have been a mistake and may have been bad judgment,” but it didn’t amount to a crime. He criticized prosecutors for leaving the court to “assume facts” about Rice’s intentions when the lieutenant decided not to restrain Gray in the van’s prisoner compartment.

“There are a number of possibilities that this court could entertain,” Williams said. “However, the burden of proof rests with the state, and the court’s imaginings do not serve as a substitute for evidence.”

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Maryland Gov. Larry Hogan (R) said Monday that he does not see the point of moving forward with the remaining trials. “It’s a waste of time and money,” Hogan said. “But that’s up to the court system to decide.”

The law office representing Rice and a spokeswoman for State's Attorney Marilyn Mosby declined to comment on Monday’s verdict, citing a gag order imposed by Williams. The Gray family attorney also declined to comment.

The police union on Monday again criticized Mosby, saying she rushed to judgment and urging her to drop the remaining cases. “The evidence hasn’t changed, and as far as I know, no new evidence is going to be presented,” Baltimore City police FOP President Gene Ryan said.

Gray’s death became a flash point in an already roiling national debate over racial profiling and the deaths of black men in police custody. Peaceful demonstrations in Baltimore gave way to riots and looting in the days after Gray’s funeral, prompting officials to impose a curfew and call in the National Guard to restore order.

Mosby announced charges against the officers in a nationally televised news conference last year, saying she would seek justice for the city’s young people. Mosby was not in the courtroom Monday, but she has been present for previous verdicts.

Rice, wearing a gray suit and a blue dress shirt, shook hands with his lawyers when the judge finished reading his decision. Co-defendants Miller, Goodson and Nero sat at the front of the courtroom; the officers patted each other on the back when the verdict came down.

In his remarks, Williams said prosecutors did not prove that Rice acted with “wanton and abandon indifference to human life” solely because he didn’t follow department orders requiring officers to seat-belt detainees. “Commission of a crime cannot simply be equated to failure to follow a general order,” Williams said.

The judge also sought to resolve some ambiguity over the scene of Gray’s arrest. Rice’s defense attorneys and prosecutors butted heads over whether a group of onlookers posed a threat to law enforcement as officers moved Gray into the van. Rice’s lawyers said a nearby apartment complex was “emptying out” and an angry crowd was cursing officers. Prosecutors contended that the scene was calm and that officers weren’t in danger.

“It’s clear that emotions and tensions ran high on April 12, 2015,” Williams said. “None of the individuals that testified indicated that it was a quiet time.”

David Jaros, a law professor at the University of Maryland in Baltimore, said Monday’s verdict will make it a challenge to convict the remaining officers, but added that it was important to consider the cases beyond a simple tally of wins and losses.

“If [a prosecutor] believes a crime was committed and they believe they’re sending a valuable message to the community about the value of a poor black man’s life or what is appropriate responsibility for a police officer, there are benefits of this trial that can’t be measured in convictions and acquittals,” Jaros said.

Baltimore Mayor Stephanie Rawlings-Blake said in a statement Monday that Rice would face an administrative review by the police department.

Outside court, about a half-dozen protesters received the news with disappointment.

Tawanda Jones, 38, a picketer who has been at each trial, stood in front of the courthouse screaming in disgust.

“Until we change these laws in place to keep these killer cops off the streets,” Jones said, “it's going to continuously happen.”

LaVendrick Smith and Ovetta Wiggins contributed to this report.