Rice was the highest ranking of the six police officers charged in the high-profile case by Baltimore State's Attorney Marilyn Mosby. Prosecutors have yet to secure a conviction.
Rice, 42, was cleared of charges including involuntary manslaughter, misconduct in office and reckless endangerment. He elected a bench trial, and Circuit Judge Barry Williams decided his fate instead of a jury.
Two other officers were previously acquitted in relation to Gray's death -- Edward Nero and Caesar Goodson Jr. Another officer, William Porter, had a mistrial last year after a jury could not reach a consensus on the charges brought against him.
Prosecutors charged that Rice showed reckless disregard for Gray when he failed to secure him with a seat belt after he helped load Gray into the police van. Gray died of injuries that he sustained while in police custody seven days after he was apprehended.
All of the officers involved in the case have pleaded not guilty. Williams previously acquitted Officers Edward Nero and Caesar Goodson Jr. of all charges. The case against Officer William Porter ended in a mistrial in December. He is scheduled to be retried in September. Officer Garrett Miller will go before a judge on July 27, and Sgt. Alicia White's proceeding begins Oct. 13.
Prosecutors failed to prove in court that Rice acted in a grossly negligent manner and was aware of the risks to Gray but disregarded them, and in addition, they failed to prove reckless endangerment, that he was aware of the risks and acted unreasonably.
Also, they were unable to prove the lieutenant corruptly failed to carry out an act required of him. Prosecutors attempted to home in on Rice’s training during the trial, saying that he should have known the consequences of failing to secure a shackled prisoner with a seatbelt, and that he intentionally disregarded the consequences.
Williams had previously dropped an assault charge against Rice, citing lack of evidence, and also dismissed one count of misconduct on the first day of the trial.
The verdict comes at a time of increasing frustrations throughout the country over recent police shootings that left Alton Sterling and Philando Castile dead.
The Baltimore Police Commissioner announced new precautions effective today that will take place today around the city, calling for all officers to patrol in teams of two, plus, there is a rule that two cars are required to respond to calls until further notice.
"The safety of our police officers is paramount to their families, our community, and me," Baltimore Police Commissioner Kevin Davis said. "Our capacity to serve relies on our commitment to keep our police officers safe as they protect our community."
In Baltimore, 65 people taking part in a march against police use of force were arrested over the weekend after they blocked part of Interstate 83, police said. Of the 65 arrested, 10 were juveniles. Those arrested were charged with failure to obey and illegally walking on a highway.
March organizers said they were rallying to create a civilian review board for police investigations. They also want to reallocate 10 percent of the city's police budget for community programs.