A federal prosecutor said Monday that six alleged rioters are guilty of charges that carry potential prison time because they joined “a sea of black masks” on the day of President Trump’s inauguration and didn’t leave after some marchers committed acts of vandalism.

Assistant U.S. Attorney Jennifer Kerkhoff admitted there is no evidence that any of the six committed vandalism in downtown Washington, and focused her opening trial remarks instead on fear the larger group caused locals as some activists damaged shop windows and vehicles.

In her opening statement, Kerkhoff used the term “sea of black masks” six times to describe a march that lasted about 30 minutes before being partially surrounded by police, who arrested more than 230 activists, reporters and legal observers.

“You don’t have to be the one who breaks the window to be guilty,” she said. By anonymizing people who did smash windows, she said, “they actively helped those with the hammers and crowbars.”

Starbucks customers dove for cover beneath tables as “plate glass windows rained down on them,” a police officer was injured as he attempted to stop someone throwing chairs, “glass bottles are being thrown at people simply standing” nearby, Kerkhoff said.

“A massive group — hundreds of people — formed a black bloc, a group dressed all alike,” she said. “This was not some sort of spontaneous gathering. This was planned. ... ‘Come to Logan Circle at 10 a.m., anti-fascist, anti-capitalism bloc, wear all black.’”

The trial is the first for alleged Trump inauguration rioters, and the courtroom ran out of seats, requiring an overflow room for journalists, interested attorneys and activists with half-shaved heads and nose rings. Unlike crowded pretrial hearings, standing was not allowed.

The initial case is a major test for prosecutors who sought to force plea deals featuring unsupervised probation by bringing charges that could carry 61 years in prison. Just 19 people took the plea deal, leaving a long series of group trials stretched over two years.

The initial six defendants volunteered for the first trial and the group includes two volunteer medics and an independent journalist. Each faces five felony destruction of property charges, a felony riot-incitement charge and misdemeanors for allegedly rioting and conspiring to riot.

Defense attorneys argue their clients' First Amendment rights to speech and assembly were violated when police mass-arrested them.

“This case is about our freedom to associate with one another," said defense attorney Steven McCool, who gave an opening statement on behalf of client Oliver Harris.

McCool said peaceful protesters who arrived “to speak out against the election of Donald Trump” could not be held accountable for a group of vandals that he estimated to be between 15-20 people.

McCool argued that police planned in advance to mass-arrest the group, playing one commander's radio dispatches, and said cops did not give marchers an opportunity to disperse and violently assaulted them with sticks and pepper spray.

“It’s easier for police to treat everyone the same, call a protest a riot and lock everyone up, than comply with the First Amendment,” he said, adding “some officers behaved improperly” but that it would be unfair to blame the entire police force for the behavior of a few.

Kerkhoff, however, described an overwhelmed police force that used restraint, with no officers pulling a gun when “several hundred charged” toward a police line after counting down from 10. She said authorities believe 50-70 people “just ran over the officers” and escaped the cordon that ended the march.

It’s unclear if the people who escaped the police cordon were primarily responsible for the vandalism that caused police to give chase. Later in the day, after the mass arrest, activists hurled bricks at police and set a limo on fire, but most if not all of the culprits were not arrested.

Kerkhoff said defendants aren’t so innocent, even if there is no evidence they personally damaged property or attacked police.

Three of the initial defendants, Oliver Harris, Jennifer Armento and Christina Simmons, wore black and changed their clothes after police surrounded the march and doused them in pepper spray, Kerkhoff said.

Two others, Brittne Lawson and Michelle Macchio, volunteered to serve as medics, she said.

“This isn’t first aid at a charity walk,” the prosecutor said. “Her role was to aid them,” Kerkhoff said of Lawson. She said that Macchio brought goggles.

Alexei Wood, a professional photographer who livestreamed the march, “did not hide his face, in fact he showed it,” Kerkhoff said. Wood says he was acting as an independent journalist, and his attorney Brett Cohen has stressed the evolving nature of journalism.

“You can hear him cheering this violence,” Kerkhoff said of Wood, who said “woohoo” during acts of vandalism, but also when police use force against the crowd. Wood and Aaron Cantu are the only remaining journalists facing charges, after many other had charges dropped.

“This is an era where everyone can be a photographer if they want and post it,” Kerkhoff said. “Video shows you what each defendant did. ... You will get to be the detectives.”

The trial is expected to last several weeks. Convictions likely would cause more people to accept plea deals and spawn years of appeals that could establish new rules regarding mass arrests and protest rights.

There are 188 other defendants with later trial dates, and the initial trial is likely to influence legal strategies.

Acquittals, meanwhile, would spur multi-million-dollar litigation. The local American Civil Liberties Union chapter has a pending lawsuit claiming false arrest, excessive force and that police performed rectal probes without changing gloves.