Police detain a protester on Jan. 20 in Washington during protests surrounding President Trump’s inauguration. (Stefan Jeremiah/AP)

Hundreds of people, wearing all black and hiding their faces, moved through more than 16 blocks of downtown Washington on Inauguration Day. Some carried hammers, crowbars and bricks. They shattered shop windows, and by the end there was more than $100,000 in property damage.

Last week, the first six people to go to trial in the case were acquitted by a jury on all the charges of rioting and destruction of property — an outcome that illustrates the challenge for D.C. prosecutors who are preparing for trials of more than 150 others picked up in the Jan. 20 mass arrest.

The six acquitted defendants said they were lawfully exercising their First Amendment right to free speech, while a few others broke away to cause damage. Prosecutors said there was no evidence to show the six participated in the destruction, but they argued that the defendants made a choice to stay with the group and provide cover for those who smashed windows and toppled newspaper boxes. At one point, a prosecutor referred to the protesters as “a sea of black masks.”

It is not clear how many of the remaining defendants authorities believe they can prove participated in — or helped plan — protests aimed at vandalism.

Legal experts said the U.S. attorney’s office in the District could weigh whether to continue moving forward on the less serious cases after the first trial’s jury rejected the government’s theory that the entire group of protesters bears some responsibility for the destruction.

Defendant Brittne Lawson, with her back to the camera, is embraced by defendant Alexei Wood after the not-guilty verdicts in the first of the presidential inauguration riot trials. (Michael Robinson Chavez/The Washington Post)

“The message from this jury is they’re not going to convict people by a guilty-by-association basis,” said Preston Burton, a former assistant U.S. attorney for the District and a partner at Buckley Sandler law firm. Burton is not involved in the cases.

A 38-year-old juror, who sought to remain private and asked not to be identified, said that during deliberations, some jurors “unloaded” because they could not hold someone responsible for the mayhem.

During the trial, the panel watched hours of video that showed the destruction and heard from employees of businesses who described their fear in those chaotic moments. In the end, the juror said, the panel concluded there wasn’t enough evidence to convict the six people before them. The decision came after a nearly four-week trial and two full days of deliberation.

“There was a frustration across the jury that we had to watch all this video about our city being torn up and destroyed and didn’t get to punish people that deserved to be punished based on evidence,” the juror said. “I’m hoping that some of the trials down the road really get some of these people that are clearly captured on video that are breaking property.”

Prosecutors allege that a group called Disrupt J20 helped plan the protests, pulling in participants from across the country.

More than 200 people were arrested. Twenty have pleaded guilty, prosecutors have dropped cases against 20 others, and the six were acquitted. The remainder are scheduled for trial, in groups of six or seven, through mid-2018.

The defendants have been grouped into four categories based on the type of criminal conduct they allegedly committed and how similar it is to that ascribed to other defendants. Those groupings are based on factors that include the “level of seriousness” and “specific acts of destruction, planning/organizing of the riot, charging the police line, etc.,” prosecutors wrote in a March court filing.

Betty Ballester, an attorney who represents a defendant scheduled to go on trial in April, said prosecutors “need to decide what’s important for them” as they continue.

“We have a good history of allowing people to protest, and I think the jury really was wondering if these people were just protesting or were they rioting. There has been a distinct separation,” she said. “If somebody threw a brick through a window and it’s on video, then that’s pretty clear that’s a destruction of property and that’s not peaceful protesting.”

Bill Miller, a spokesman for the U.S. attorney’s office, declined to comment on the government’s case.

In a statement released after the acquittals, the U.S. attorney’s office said the damage done that day “impacted many who live and work in the District of Columbia, and created a danger for all who were nearby.”

“We appreciate the jury’s close examination of the individual conduct and intent of each defendant during this trial and respect its verdict,” the statement said. “In the remaining pending cases, we look forward to the same rigorous review for each defendant.”

Elizabeth Lagesse, a defendant who is scheduled for a trial in July, said she feels “cautiously optimistic” after the Dec. 21 verdict. She said she traveled from Baltimore to the District to protest Trump’s victory and then “got swept up in this crazy police battle basically, and then we just were held on the street for hours.”

It is “chilling” that prosecutors are holding the group liable for violence not all committed, she said.

“You only have control over what you yourself do,” Lagesse said. “Now that there’s been a jury of ordinary D.C. residents who you know just didn’t buy it, it’s time that we start dropping these charges.”

David LaBahn, president of the Association of Prosecuting Attorneys and a former deputy prosecutor in California, said to win the upcoming cases, prosecutors need to be able to explain to a jury: “What’s the culpability? . . . Of the 200, why am I sitting in judgment of this man or woman?”