Officer Caesar Goodson Jr., center, one of six Baltimore city police officers charged in connection to the death of Freddie Gray, leaves the courthouse after the second day of his trial, on June 10 in Baltimore. (Jose Luis Magana/AP)

The state’s expert on police policy and practices testified that he could not say definitively that Freddie Gray got a “rough ride” the day he suffered a fatal spinal injury in the back of a van on the way to jail.

Former Baltimore City police commander Stanford Franklin struggled to clearly define “rough ride” during his two hours on the stand Wednesday and said most of his expertise on the matter is rooted in anecdotal stories he heard from citizens during his time in law enforcement.

Franklin’s testimony came shortly before prosecutors rested their case on the fifth day of proceedings in the trial of Officer Caesar Goodson Jr., the only one of six officers in the Gray case to face a murder charge.

Prosecutors are attempting to convince a judge that Goodson is responsible for Gray’s death by failing to put Gray in a seat belt and ignoring his requests to go to a hospital. They say Gray got a “rough ride,” bouncing around in the back of the van with his hands and feet shackled, as Goodson drove recklessly.

Defense lawyers contend that there is no evidence of a “rough ride.” They said that detainees were rarely seat-belted and that it would have been unreasonable for officers to have entered the narrow van compartment to buckle Gray, because he had been combative.

Six Baltimore police officers were charged after Freddie Gray’s death and arrest. Here’s who they are. (Claritza Jimenez,Erin Patrick O'Connor/The Washington Post)

Goodson, 46, is charged with second-degree depraved-heart murder, manslaughter, assault, reckless endangerment and misconduct in office. He has waived a jury trial, opting instead to have his case heard by Judge Barry G. Williams.

Goodson’s attorneys are expected to launch their defense Thursday after Williams considers their written motion for acquittal.

Franklin’s testimony Wednesday could be a blow to prosecutors, who have yet to secure a conviction in the Gray case. Franklin initially defined a “rough ride” as “a term used to describe a ride given to someone transported in one of our vehicles.”

When later pressed, he said that a rough ride also included “sudden accelerations, sudden stops, quick turns,” but testified he saw none of those things based on the tapes and evidence he reviewed in the Gray case.

“Is it not your contention that officer Goodson engaged in a rough ride?” Goodson’s attorney Matthew Fraling asked Franklin during a sharp cross-examination.

“I can’t say,” Franklin responded.

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Franklin said there would have been no risk to Goodson by putting Gray in a seat belt. And buckling Gray could have prevented his injury, Franklin said.

“Your ability to prevent yourself from being a projectile in that van is very limited” without a seat belt while your hands and feet are shackled, Franklin testified.

Also on Wednesday, Williams found prosecutors again violated discovery rules by failing to submit notes from a detective who met with medical examiner Carol H. Allan.

Allan had testified last week that she never believed Gray’s death was an accident, saying, “The word ‘accident’ never crossed my lips other than to say, ‘This was not an accident.’ ” But notes the detective took during a meeting with Allan say she indicated at one point that Gray’s death may have been an accident, Williams said.

As a remedy for the most recent discovery violation, Williams said he would allow Goodson’s attorneys to call the detective as a witness and submit her notes as evidence.

Prosecutors produced the detective’s notes after Williams last week ordered the state to reexamine their evidence to see whether any remaining material had not been turned over to the defense. The judge ordered the review after he found that the prosecution had withheld other evidence that could benefit Goodson.

Whether Gray’s death in police custody was an accident is an important part of determining whether officers charged in the case are criminally responsible.

Police arrested Gray the morning of April 12, 2015, after he made eye contact with officers and fled. He was loaded into a police van to be taken to central booking. The medical examiner’s report suggests Gray’s spine injury probably occurred when the van made an abrupt stop or turn and Gray, unable to brace himself, fell and struck his head.

Allowing the defense to call on the detective is out of the ordinary but appropriate, Williams said, “because of the failure of the state to turn over information in a timely manner.”

Goodson is the third officer to go to trial, following Officers William Porter and Edward M. Nero. Porter stood trial in the same court last year, but a jury failed to reach a verdict. He is scheduled to be retried in September. Nero was acquitted in May of assault, reckless endangerment and misconduct in office.