Officer Edward Nero, from left, Lt. Brian Rice and Sgt. Alicia White, three of six Baltimore city police officers charged in connection to the death of Freddie Gray, leave the Maryland Court of Appeals on March 3 in Annapolis. (Jose Luis Magana/AP)

A little more than a year after the fatal injury of Freddie Gray in police custody and the riots that set Baltimore aflame, the second of six officers charged in the case is set to go to trial.

Prosecutors and defense attorneys will argue over whether Edward M. Nero — one of the first police officers to encounter Gray that April day — illegally arrested the 25-year-old in West Baltimore and whether Nero’s actions amounted to an assault.

The way prosecutors see it, Gray never should have been handcuffed and placed in the police van where he suffered a fatal injury. The officers had no probable cause to arrest him, prosecutors contend in court papers, and “without the legal justification needed to detain a citizen, any amount of force is excessive.”

Defense attorneys counter that officers making instant decisions on street patrol sometimes make arrests that are later questioned. In those cases, they say, the charges should be dropped or evidence suppressed. “Common sense dictates that officers would simply not make arrests if they were subject to criminal prosecution if it was later determined that probable cause did not exist,” the defense wrote in court papers.

The prosecution theory is highly unusual and could have sweeping implications for policing if officers become worried that good-faith actions on the job will subject them to criminal liability, according to legal experts.

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“If they’re going to go back and review my actions like that and then charge me even if I had the right, I’m not going to make the arrest,” Baltimore criminal defense attorney Warren Brown said of the possible concerns police would raise if Nero is convicted. “If I’m not going to make any arrests, public safety has been jeopardized.”

Gray’s death sparked protests and then riots across the city and fueled national controversy over the deaths of young black men in police custody. The trial of the first officer charged in the case ended in December in a mistrial.

Gray was arrested April 12, 2015, after he made eye contact with police in his West Baltimore neighborhood and ran. Nero was one of the officers who chased and detained Gray, handcuffing and holding him down. After finding a knife in Gray’s pants pocket, police put him in the back of a police van, where he suffered a serious neck injury. He died one week later.

Court documents suggest prosecutors will argue that the knife taken from Gray was lawful and, therefore, there was no reason to arrest him. Under the Baltimore City code, the spring-assisted knife is not allowed, but it is not a violation of Maryland law to possess it.

“The state has charged the Defendant with assaulting Mr. Gray by intentionally inflicting upon him the offensive physical contact of the force the Defendant used to arrest Mr. Gray without probable case,” prosecutors wrote in court filings. “The police officer’s privilege to use force in the exercise of his duties is just that — a privilege, not a right.”

But Nero’s attorneys said they could not find a single case in Maryland or elsewhere in the country where a police officer has been charged “solely on the basis” of an arrest that allegedly lacked probable case.

A pedestrian walks by a mural portraying Freddie Gray on April 21 in Baltimore. (Matt McClain/The Washington Post)

Defense attorneys have subpoenaed several prosecutors in the charging division of the Baltimore City State’s Attorney’s Office and are expected to ask them why they have never charged a police officer for an illegal arrest before.

A gag order prohibits prosecutors and Nero’s attorneys from speaking to the media.

Police officers often detain people who are later found not to have committed any crime, and charges are dropped. For example, sometimes people are arrested on drug charges, but lab testing reveals the substances they had weren’t illegal. But rarely does anyone charge an officer afterward for an illegal arrest, said Roya Hanna, a Baltimore defense attorney and former city prosecutor.

“This just could come down to a legal issue about whether officers can be arrested for doing what they believe was their duty,” Hanna said. “But by that logic almost everyone who has made an arrest that a judge later finds no probable cause for would be arrested.”

Detaining citizens, however, should not be taken lightly, said Tessa Hill-Aston, president of the Baltimore NAACP.

“Freddie ran because that is what African American men and young boys do in that community,” Hill-Aston said. “You can’t throw everybody down and then say, ‘Let’s see what they got.’ It doesn’t happen in the white neighborhoods.”

A motions hearing for Nero’s case is set for Tuesday, and the trial is set to start Wednesday. Prosecutors have requested the trial be pushed back to Thursday because the state’s attorney’s office suffered electrical problems that delayed final preparation.

The trial of Officer William G. Porter ended in December. Nero’s trial could end with a decisive conviction or acquittal if the officer opts for a trial by judge instead of jury.

Baltimore defense attorney Jeremy Eldridge said it is to Nero’s advantage to have a judge render a verdict, since the trial will focus on nuanced legal matters in an emotionally charged, highly publicized case.

“A judge is not going to be emotionally swayed by some of the public sentiment in the same way you may worry with a jury,” Eldridge said.

While Nero, charged with second-degree assault, two counts of misconduct in office and reckless endangerment, doesn’t face the gravest charges of the six officers charged, many members of the public see him and others who arrested Gray as most culpable.

“Even through the prosecution of them is the least warranted, they are the faces of this whole thing,” Brown said. “For a large segment of the African American community, they see that this is where the damage is done.”

Medical experts and an autopsy report said Gray suffered his fatal injury after he was loaded in the police van. But the arresting officers — who are white — are the ones seen on viral video sitting on Gray, digging a knee into him and dragging him, limp-legged and screaming, to the van.

Many, including Hill-Aston, are still convinced that Gray was injured before he got into the van.

“Most people who may not have been in the courtroom or read the newspaper, if you’re sitting in your house looking at the video, you’re going to say, ‘Oh my God, that boy is injured,’ ” Hill-Aston said. “Everyone has different opinions about what they think. The bottom line is he is deceased and it shouldn’t have happened in the first place.”