BALTIMORE (Reuters) - A Baltimore police officer fatally injured black detainee Freddie Gray by giving him a “rough ride” in a transport van, a prosecutor said on Thursday in opening statements of the murder trial of a third officer in Gray’s death.

A lawyer for Officer Caesar Goodson Jr., 46, said in Baltimore City Circuit Court that Gray’s death in April 2015 was accidental and that Gray caused his own injuries.

“There will be no evidence showing he gave a rough ride or drove improperly,” defense attorney Andrew Graham said at the start of what is considered the highest-profile trial in the case.

Goodson drove the police van in which Gray suffered a broken neck. His death a week after being arrested triggered protests and rioting in Baltimore and stoked a U.S. debate on police treatment of minorities.

Goodson is accused of second-degree depraved heart murder, the most serious charge against the six officers accused in Gray’s death. He also faces manslaughter and other charges.

Prosecutor Michael Schatzow said Goodson bounced Gray around by driving unsafely in retaliation for him yelling and kicking inside the van. Gray had been arrested for fleeing officers unprovoked in a high-crime area.

Goodson failed to follow procedures when Gray was put in his van while shackled and was not secured with a seat belt, Schatzow told Judge Barry Williams, who is hearing the case in a bench trial.

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Goodson also stopped the van at one point and saw that Gray was injured, he said

But Graham said Goodson had driven cautiously and Gray was injured because he thrashed around and stood up in the back of the van.

Initial testimony focused on training and procedures. Police Captain Martin Bartness, who had helped draft seat-belting guidelines, said under questioning by Schatzow that van officers were responsible for detainees in their vehicles.

In cross-examination by Graham, Bartness said that officers were not trained in medical diagnoses and that department manuals said that officers could use their own discretion.

Before opening statements, Williams criticized prosecutors for withholding evidence. Prosecutors had failed to give the defense material from a May 2015 interview with Donta Allen, who was put in a separate van compartment after prosecutors contend Gray was injured.

Williams said Schatzow would face sanctions. He ordered the prosecution to turn over all material to lawyers for Goodson and the officers still facing trial.

The trial of one officer in Gray’s death ended in a hung jury. Williams issued an acquittal in a second one.