Jurors in Colorado on Friday ordered the city and county of Denver to pay $14 million in damages to 12 plaintiffs after finding that police officers used excessive force against them during demonstrations over the killing of George Floyd in 2020.

The civil case in the U.S. District Court of Colorado was the first in the nation in which a lawsuit accusing the police of misconduct during the 2020 protests went to trial, according to the plaintiffs’ lawyers, who added that it could set a precedent for other pending cases across the country involving police misconduct against protesters in the George Floyd demonstrations.

The jury of eight Coloradans concluded that the city and county failed to properly train its police and that as a result, officers violated the plaintiffs’ constitutional rights under the First and Fourth Amendments.

“The verdict is a message to the police department, to the highest echelons of the police department, but also a message to police departments all over the country,” said Mark Silverstein, legal director with the American Civil Liberties Union of Colorado, which represented the plaintiffs in the case.

The verdict followed three weeks of presentations involving expert testimony, firsthand accounts from the police and protesters, and video from body cameras and cellphones.

The police shot at the plaintiffs with projectiles at close ranges without warnings, striking some of them, according to the complaint, which was filed by the A.C.L.U. of Colorado and attorneys with the firm Arnold & Porter. Officers also used pepper spray and tear gas, among other tactics, on the plaintiffs, the complaint said. One protester, Zach Packard, was hit in the head by a projectile, knocking him unconscious and sending him to the I.C.U. He received the largest damage amount, $3 million.

Another plaintiff, Dr. Stanford Smith, was talking with other protesters near a park when an officer left a police line and sprayed Dr. Smith directly in the face with pepper spray, without warning, the complaint said.

“I feared for my life, because I couldn’t see, I couldn’t breathe,” Dr. Smith recalled in an interview Saturday. The protest was the first he had ever attended, he said, having made his way there from the library where he was studying for his board examination as a dental student.

He said he had been offered a settlement but was determined to bring the case to trial.

“What the police did was wrong, and we wanted the facts to come out in court,” said Dr. Smith, adding, “This was never about a monetary settlement. To me it was more so about trying to create a way and a system that police are actually held responsible for their actions.”

The city and county of Denver acknowledged shortcomings in how the police responded to the protests but argued that the demonstrations caused a “level of sustained violence and destruction” that the city had never seen.

In a statement, the Denver Department of Public Safety, which includes the police department, said: “We were prepared for a worst-case scenario, but we weren’t fully prepared for what transpired. Unfortunately, Denver Police Department officers and other law enforcement officers responding to assist encountered extreme destructive behavior from some agitators among largely peaceful protesters. We recognize that some mistakes were made.”

The Denver Police Department has changed its protest response plans in the years since, according to the Department of Public Safety, including eliminating the use of certain projectiles and instituting additional crowd control training.

Between late May and the end of August in 2020, protesters clashed with police departments in hundreds of cities across America. In Philadelphia, the police sprayed tear gas on a crowd of mainly peaceful protesters trapped on the side of a highway. Los Angeles officers were given only two hours of training in using highly technical foam-projectile launchers for crowd control, one of which bloodied the eye of a homeless man in a wheelchair. Across the country, at least eight people were blinded after being hit with police projectiles.

In city after city, after-action evaluations concluded that police forces were poorly trained for the demonstrations and criticized them for heavily militarized responses. While many police departments allow that reforms are needed, they have also said that officers were asked to confront chaotic crowds that sometimes attacked the police, and that they were responding to demands to maintain order by residents, business owners and elected officials.

Countless lawsuits have been filed by protesters across the country, including many class-action suits representing dozens of protesters and residents. In some, judges have cleared the cases to go to trial, but court proceedings and appeals can extend the process for months or longer, and the parties can still settle, which is common in federal civil rights cases.

Denver officials have already settled several protest-related lawsuits and paid more than $1.3 million to injured demonstrators, according to the Department of Public Safety. The city of Columbus, Ohio, reached an agreement in 2021 to pay $5.75 million to 32 plaintiffs who said police officers had injured them and violated their constitutional rights during protests.

Police reform advocates say they hope that the Denver verdict will not only serve as a precedent for other cases if they go to trial, but will put pressure on legislators to pass measures that address excessive force.

“Their job is not done, and in fact it has only begun,” said Udi Ofer of the A.C.L.U.’s National Political and Advocacy Department, adding, “We hope that this verdict will help regain attention to not only the inappropriate treatment of protesters but also as a reminder to the nation abut the underlying concerns that people across the nation were protesting about.”