A white Baltimore police officer failed to follow procedures in the arrest that led to the death of Freddie Gray from a broken neck, a prosecutor said on Thursday at the start of the officer's trial.

A lawyer for the officer, Edward Nero, said, however, that he had little to do with Gray's arrest and transport in a police van. Gray, a 25-year-old black man, died in April 2015 from a spinal injury suffered in the vehicle.

Nero, 30, is the second officer to face trial in Baltimore City Circuit Court for Gray's death.

The death sparked rioting and protests across the majority-black city of 620,000 people. The incident is one of those highlighted by the Black Lives Matter movement.

Prosecutor Michael Schatzow said in opening arguments that Nero, among three bicycle officers who chased and arrested Gray when he fled unprovoked, had no idea why Gray was being pursued.

That made his arrest illegal, Schatzow said. Court papers say officers found a spring-assisted knife in Gray's pocket.

Nero and a second white officer, Garrett Miller, planned to arrest Gray and then determine what to charge him with, Schatzow told Judge Barry Williams, who is presiding over a bench trial.

Nero failed to secure Gray in the van despite a department memo underscoring that detainees had to be seat-belted, Schatzow said.

But Marc Zayon, Nero's lawyer, said Miller had made the arrest and handcuffed Gray. Nero never put hands on him except to help find Gray's asthma inhaler when he asked for it, Zayon said.

The responsibility to secure Gray in the van belonged to Miller and its driver, African American officer Caesar Goodson Jr., Zayon said.

The first prosecution witness was Captain Martin Bartness, the police commissioner's chief of staff. He testified that officers were expected to follow policies, such as buckling suspects into the van.

Other witnesses included a former police trainer, a crime lab technician who took photos of the van, a city official who testified about van seat belt purchases and an officer who showed how a detainee could move around in the van.

Nero faces misdemeanor charges of second-degree assault, two counts of misconduct in office and reckless endangerment.

Five other officers face charges, ranging from misconduct in office to second-degree murder. The first trial, that of African American officer William Porter, ended in a hung jury in December.

(Writing by Ian Simpson in Washington; Editing by Bernard Orr and Steve Orlofsky)