A former Louisiana state trooper was acquitted on Wednesday of a charge that he violated the civil rights of a Black man when he repeatedly clubbed him with a flashlight after a traffic stop more than four years ago.

The case, involving the former trooper Jacob Brown, drew national attention and outrage after police body-camera footage of the beating emerged. The footage showed Mr. Brown striking Aaron Larry Bowman about 18 times in the head and chest with a flashlight, while Mr. Bowman was pinned to the ground after a traffic stop in May 2019. Mr. Bowman sustained a broken jaw, three fractured ribs, a broken wrist and a gash to his head requiring staples.

In the body-camera video, which was obtained and published by The Associated Press, Mr. Bowman can be heard pleading with the trooper between blows, saying, “I’m not resisting.”

Mr. Brown, now 32, was found not guilty of depriving Mr. Bowman of his civil rights after a three-day trial in Monroe, La., about 100 miles east of Shreveport. Mr. Brown previously told investigators that he had used a flashlight as a baton, as part of what he called “pain compliance.” Federal prosecutors had described the flashlight as having a metal tactical cap designed for breaking glass.

In response to the jury’s decision, Brandon B. Brown, the U.S. attorney for the Western District of Louisiana, said on Thursday, “We believe that this victim’s civil rights were violated.”

“Unfortunately for us, the jury didn’t agree, and we’ll have to respect their decision,” he said.

After the verdict, Ronald S. Haley, a lawyer for Mr. Bowman, said “we are definitely disappointed and believe that officer Brown should have been found guilty of the charges.”

“It does go to show that it is extremely difficult to get a federal civil rights violation on an officer because they have to prove beyond a reasonable doubt, willful intent and bias,” Mr. Haley added.

Scott Wolleson, a lawyer for Mr. Brown, said in a statement on Thursday that his client “was completely vindicated.”

He added: “The men and women of the jury recognized the risks law enforcement officers like Jacob Brown face on our behalf every day.”

If convicted, Mr. Brown would have faced up to 10 years in prison, three years of supervised release and a fine of up to $250,000.

An offense report filed with the Ouachita Parish Sheriff’s Office said that Mr. Bowman had ignored the lights and sirens of a deputy who tried to pull him over after the S.U.V. Mr. Bowman was driving had crossed the centerline of a road. The deputy said that Mr. Bowman had struck him on the head with a closed fist and had put up a struggle after telling the police he had been afraid to pull over and wanted to park the vehicle at his home in case he went to jail.

A spokeswoman with the Louisiana State Police later said that an investigation had determined that Mr. Brown’s body-camera footage had been “intentionally mislabeled.”

Mr. Haley said that Mr. Bowman had not recovered mentally from the incident.

“Physically, he has recovered to the extent that the headaches aren’t as bad as they were,” Mr. Haley said, but “he still suffers from trauma. He still has some permanent scarring” that he believes will serve “as a reminder as to what happened to him that evening in May 2019.”

While the civil rights case involving Mr. Brown has come to a conclusion, state and federal prosecutors are still investigating another case: Ronald Greene, a Black man who died in 2019 in the custody of Louisiana State Police. Body-camera video of that police encounter showed officers punching, dragging and using a stun gun on Mr. Greene, who screamed out that he was sorry and that he was scared.

The case fueled activists and drew widespread scrutiny of the Louisiana State Police after an initial description of Mr. Greene resisting arrest after a high-speed chase was unraveled by body-camera footage.

In December, five law enforcement officers were charged in connection with the violent encounter. One of the officers was charged with a single count of negligent homicide.

Johnny Diaz contributed reporting.