This will be no ordinary trial, set to begin Monday before Judge Lynn Leibovitz in D.C. Superior Court. It is unusual not only for the abundance of young activists who showed up to watch jury selection — earnestly scribbling notes in support of the accused — but because the six defendants are the first to be called to be accountable in a fiery, glass-shattering civil disturbance on President Trump’s Inauguration Day.

Many more trials stemming from the rioting could lie ahead.

The protesters called their Jan. 20 demonstration “Disrupt J20.” By the hundreds that morning, clad in dark clothing, their faces hidden, they marched from Logan Circle to the Franklin Square area in downtown Washington. They came in waves, smashing windows, painting graffiti, toppling newspaper ­boxes and setting mostly small fires — except for a blaze that consumed a limousine.

Now, prosecutors plan to have their say. The defendants face felony charges of inciting a riot and destruction of property, with each offense punishable by up to 10 years in prison. As for others arrested in the mayhem that day, the U.S. attorney’s office said it intends to put more than 150 additional defendants on trial in groups of about a half dozen, a process that could stretch into the middle of next year.

Protesters set fire to a limousine on Inauguration Day in Washington. (Matt McClain/The Washington Post)

To the government, the case is strictly about a breach of law and order, an alleged instance of organized, premeditated property destruction.

But activists in the courtroom called it a stifling of free speech and a draconian effort by authorities to enforce collective responsibility.

“The repression of dissent against Trump has been rife in this case,” the defendants’ supporters said in a statement. The group’s spokesman noted that the four women and two men on trial are not alleged to have personally caused any damage. Instead, they are accused of taking part in a demonstration that they knew was organized for the purpose of wreaking havoc in the city, including costly vandalism.

“This case could have many implications for the future,” the statement said, “as the prosecution is attempting to establish a conspiracy based on clothing, chanting, and the same sort of organizing that goes into any march or protest.”

In the days before the inauguration, authorities said, undercover D.C. police officers infiltrated meetings of Disrupt J20 members at which the rioting was planned.

During and after the disturbance, more than 200 people involved in the protest were arrested, police said. The U.S. attorney’s office said 20 defendants pleaded guilty to reduced charges in deals with the government and another 20 cases were dismissed.

Whether the U.S. attorney’s office will go through with its plan for multiple trials remains to be seen. Authorities have said that one purpose of the aggressive prosecutions is to send a message to would-be rioters that the city will respond decisively. But if the defendants mostly prevail in the early trials, it is possible that the government will rethink how it handles the rest.

Media and protesters move through the smoke of concussion grenades during clashes on Inauguration Day. (Jahi Chikwendiu/The Washington Post)

The U.S. attorney’s office declined to comment on that issue.

Sixteen jurors, including four alternates, were picked for the first trial, with opening statements set for Monday.

Leibovitz ruled that to secure guilty verdicts on the rioting counts, the government will have to do more than show a defendant took part in the protest. There must be proof that he or she helped organize or incite the mayhem, the judge said. Prosecutors said they will rely heavily on digital evidence, including social media postings, Internet mes­sages and video from cellphones and police body cameras.

For alleged rioters who the government says were dressed like ninjas and bent on tearing up the city Jan. 20, the six defendants appeared composed and studiously attentive in the courtroom during two days of tedious jury selection. On Thursday, the men wore dress shirts, suit coats in shades of gray, and quiet ties. The women’s attire included pantsuits, a skirt, a powder blue sweater and subdued blouses.

It was hard to distinguish them from their lawyers, although Alexei Wood, 37, of San Antonio, showed a flourish. He chose a light-gray pinstriped suit with coordinated shirt and neckwear, accented by canvas sneakers — one black, one purple.

The other defendants are Michelle Macchio, 26, of Naples, Fla.; Christina Simmons, 20, of Cockeysville, Md.; Brittne Lawson, 27, of Pittsburgh; and Jennifer Armento, 38, and Oliver Harris, 28, both of Philadelphia.

About two dozen of their supporters, nearly all millennials, sat in the gallery, some holding ­college-ruled notebooks. They wrote furiously, recording the responses of prospective jurors as Leibovitz asked about hardships or potential biases.

For young activists, they were remarkably disciplined about not saying a word to the press. In declining to be interviewed, most just turned away, adamantly shaking their heads.

One women in the back row of the gallery Thursday — sipping from a Mason jar and hoping the courtroom marshals wouldn’t notice — said quietly, “You can talk to Kris,” and pointed to a middle-aged man in a blue plaid shirt, a few benches away.

Who is Kris? . . . But this was too much to ask.

“He’s Kris,” was all she would whisper. “Kris is Kris.”

Kris is Kris Hermes, 53, an activist from the San Francisco Bay area and the leading organizer of the support group Defend J20. In a courthouse hallway, explaining why the younger people had been instructed to keep quiet, he said, “We wanted to make sure our message is coherent and accurate.”

He said the message is: “People are being railroaded in this case. What the government is saying to us is, dissent is not an acceptable form of expression in this country, and if you choose to go out on the street and express yourself, then you risk being arrested and seriously prosecuted. And we’re trying to push back against that.”

Meanwhile, jury selection dragged on. On Wednesday, scores of prospective jurors listened to questions from Leibovitz and jotted their answers on index cards. Then, individually, they were called into the courtroom to be questioned further by the judge. The process went on for hours, until early Thursday afternoon, and, at times, it seemed to test even Leibovitz’s patience.

One by one, each walked in and approached the judge.

Here was a pregnant woman who said she needed hot food every two hours.

When she was gone, the judge sighed, looked at the lawyers and said: “Is there something that’s changed in the last 28 years that you have to have a hot meal every two hours when you’re expecting a child? I don’t know. . . .”

Here was an international lawyer whose answers were exceedingly precise.

After he left, Leibovitz had a warning for the trial attorneys: “I just want to say, if you don’t want deliberations to take the rest of our lives, he should stay off the jury.”

And here came a young man in baggy jeans and a Batman T-shirt, sauntering up the aisle toward Leibovitz, carrying a half-empty bottle of Schweppes ginger ale.

“How are you, sir?” she said pleasantly.

“How you doing, judge?”

And he was excused moments later, after he told Leibovitz: “You know, you go back to that date, and from where I stand, I’d probably be in the riots, too, but I was busy. You know, to be honest with you, I’m with the cause.”