BALTIMORE - Prosecutors say a policeman charged in Freddie Gray's arrest committed a crime when he and two other officers detained and handcuffed him without probable cause after he ran from them in a high-crime neighbourhood. The officer's defence attorney says the law allows for such a stop.

The trial for Officer Edward Nero, 30, who faces assault, misconduct in office and reckless endangerment charges, is raising broad questions about alleged police misconduct and the balance between officers' authority to detain suspects in a city riddled with crime and violence, and their professional obligation not to abuse their power at a time when trust between the police and the community remains fractured from decades of problematic practices.

A Baltimore judge will ultimately decide the officer's fate Monday. While legal experts say the prosecutors' case may not hold water, the social implications of their arguments are significant.

"It was somewhat satisfying to see a prosecutor challenge problematic police behaviour, that on a regular basis citizens are being detained and mistreated without probable cause," said David Jaros, an assistant professor of law at the University of Baltimore who sat through much of Nero's trial. "That's a powerful statement."

Grey died April 19, 2015, a week after his neck was broken in the back of a police transport van while he was handcuffed and shackled, but left unrestrained by a seat belt. His death prompted protests that gave way to looting, rioting and arson across vast swaths of the city. While Gray's injury was the focus of the first officer's trial late last year, Nero's case has focused on the initial arrest.

During closing arguments, Baltimore Circuit Judge Barry Williams grilled prosecutors, asking if every officer who makes an arrest without probable cause should face criminal charges rather than simply release the suspect later or suppress whatever is found during a search of the person.

Assistant State's Attorney Jan Bledsoe said it depends on the circumstances, but told the judge that such a scenario happens every day in Baltimore, and should be taken seriously.

"That's what happens in the city all the time," she said. "People get jacked up."

Nero's defence attorney Marc Zayon said the officers acted reasonably that day, and Gray's flight in a designated high-crime area justified his detention. Even if the detention had been wrong, Zayon said, the officer still shouldn't be charged criminally.

"Being detained is a horrible thing," Zayon said. "Being handcuffed is a horrible thing. Being put in a prone position is a horrible thing. But the law allows it."

Jaros said that prosecuting an individual officer in order to indict the practices of the police department as a whole may not be appropriate, but the sentiment is important to address.

"There are too many arrests and they lack probable cause, and individuals are stopped and frisked without reasonable suspicion. But that being said, I think there's very little evidence in the record that what happened in the course of this detention rose to the level of criminal activity that would justify an assault charge."

Prosecutors say Nero was reckless and negligent when he failed to buckle Gray into a seat belt despite a departmental general order requiring that all prisoners be properly secured during transport. The defence called a number of witnesses to testify that officers routinely ignore the order, and ultimately have discretion over whether to buckle an inmate despite the policy.

"General orders aren't laws," Zayon said during closing arguments. "They're not in the criminal code."

Doug Colbert, a professor at University of Maryland Francis King Carey School of Law also observed Nero's trial, said officers disobeying a departmental order shows systemic issues.

"The notion of reasonableness -- is it reasonable because that's how the police do it, or because it's right?" he said. "There's almost a power struggle here between the union wanting the officers to make the final decision, and a police commissioner wanting uniformity in how officers police."

Warren Alperstein, an attorney who is unaffiliated with the case but watched it from the gallery, said policy issues have no place in the courtroom.

"When the state appeared to argue that this case would send a message to other Baltimore city police officers that arresting citizens without justification will result in prosecution of the officers, Judge Williams made it clear that he was judging this case solely on the facts of this case and the law that applies, and won't be motivated by the states' public policy desires or interests," he said.

News from © The Associated Press, 2016