Lt. Brian Rice, second from left, arrives at the courthouse in his trial in Baltimore. (Patrick Semansky/AP)

Lt. Brian W. Rice bears responsibility for the death of Freddie Gray, prosecutors argued Thursday, because he was the highest-ranking officer at the scene the day the young man was fatally injured in policy custody.

Gray’s death last year came amid a fevered national debate over fatal police encounters with black men, and it sparked demonstrations and later riots in Baltimore. Protesters cheered when city State’s Attorney Marilyn J. Mosby promised justice and charged six officers who had been involved in Gray’s arrest. But two officers have now been acquitted by the same judge who will decide Rice’s fate, and prosecutors have yet to secure a conviction in the case.

At issue is whether Rice and other officers should have seat-belted Gray, 25, in the back of a police transport van after his arrest in April 2015. Instead, Gray was put on his stomach on the floor of the van with his hands cuffed behind his back and his legs shackled. After the van made several stops in West Baltimore, Gray was found unconscious inside. He had suffered a severe neck injury and died a week later.

Prosecutor Michael Schatzow said in opening statements that Rice’s rank separated him from the other officers involved in Gray’s arrest and transport. As a lieutenant, Schatzow argued, Rice would know that seat-belting was mandated and had the responsibility to order it.

“Because of decisions that Lieutenant Rice made, Mr. Gray is dead,” Schatzow said. “This defendant is not an inexperienced officer who was ignorant of the rules that governed his conduct. . . . He knew he was required to use [a seat belt] on Mr. Gray. He knew it, and he ignored it.”

Events leading to Freddie Gray’s death, explained in augmented reality

But defense attorneys countered that Rice’s 18 years on the force led him to conclude that Gray’s “belligerent” behavior that day made it too dangerous for officers to seat-belt him in the narrow van compartment.

Rice, 42, faces charges of manslaughter, reckless endangerment, assault and misconduct in office. Before the proceedings began, prosecutors dropped a misconduct in office charge related to Gray’s arrest.

Prosecutors will present their evidence to the same Baltimore City Circuit Court judge, Barry G. Williams, who has acquitted two of the six officers charged in the case. Like those two officers, Rice has requested a bench trial, in which the judge decides the verdict. The first trial in the case ended in a hung jury.

Gray’s arrest unfolded the morning of April 12, 2015. While on bike patrol in West Baltimore, Rice saw Gray run and called for officers to give chase. After a brief pursuit, Rice helped other officers shackle Gray’s wrists and legs and load him on his stomach into a police van without a seat belt. Gray had interactions with officers at several stops but was unresponsive when they arrived at the Western District police station.

Unlike the other officers who have faced trial, Schatzow said, Rice had his own computer and thus could not claim to be unaware of a policy issued just a few days before Gray’s arrest requiring that all detainees be seat-belted.

Defense attorney Chaz Ball countered that police at the time routinely transported unrestrained detainees and that Rice “made a nine-second assessment that it was too dangerous to try to force Mr. Gray into a seat belt.”

A mural of Freddie Gray at the Baltimore intersection where he was arrested. (Patrick Semansky/Associated Press)

Ball repeatedly used the phrase “banging and belligerent” to describe Gray’s behavior during his arrest, saying that he was deliberately trying to incite a crowd that had gathered as officers placed him in the van.

As a lieutenant, Rice understood the dangers of a combative detainee better than the other officers on the scene, Ball said, and made an “absolutely, 100 percent reasonable” decision not to seat-belt Gray in the cramped transport van.

“Mr. Gray’s death was a tragic freak accident that nobody could have foreseen,” Ball contended.

A challenge prosecutors have faced in each trial has been the lack of clarity about when Gray was injured. Cameras in the wagon were not working. Carol Allan, the medical examiner who performed Gray’s autopsy and ruled his death a homicide, testified that she believed his injury occurred during the middle of the ride to the police station. But she acknowledged, “There are no witness statements, and there is no video.”

Defense attorney Michael Belsky pressed Allan on why she dismissed the testimony of an officer who said Gray didn’t show signs of medical distress until the van arrived at the final stop.

“I don’t expect untrained individuals to make medical decisions,” Allan said, adding that Gray’s injuries would have manifested internally at first. She said she came to believe that Gray broke his neck somewhere in the middle of the trip because that’s when he stopped moving and kicking in the van and asked for medical attention.

Rice’s trial comes just weeks after Williams acquitted Officer Caesar R. Goodson Jr., the van’s driver, on all counts, including second-degree depraved-heart murder. Prosecutors alleged that Goodson gave Gray a “rough ride,” driving recklessly as Gray was tossed around in the van’s prisoner compartment. He faced the most serious charges in the case.

Officer Edward M. Nero was acquitted in May of assault, reckless endangerment and misconduct in office after a bench trial. Officer William G. Porter is scheduled to be retried in September, after a jury failed to reach a verdict on his charges late last year.