WASHINGTON (CN) — Federal prosecutors will drop charges against 129 of 188 people who were accused of felony rioting after President Donald Trump’s inauguration last year, the U.S. Attorney’s Office for the District of Columbia said Thursday.

Prosecutors will still press cases against 59 defendants they contend were most responsible for the demonstrations, which resulted in smashed windows, property damage and some violent clashes with police. Prosecutors claim protesters used “black bloc” tactics, referring to a group known to show up at peaceful protests wearing all black in hopes of stirring up chaos.

A grand jury returned an indictment against 215 people in April last year, charging each with five counts of felony destruction of property and one count each of felony urging or inciting a riot, engaging in a riot and conspiracy to engage in a riot. Twenty people have pleaded guilty.

ACLU senior staff attorney Scott Michelman said in a statement: “The U.S. attorney has essentially admitted it never had the evidence to charge these innocent people in the first place, and we’re gratified to see they’ve come to their senses.

“For a full year, the government’s abusive prosecution has upended the lives of these defendants, who’ve endured the anxiety of multiple court hearings and suffered disruptions to their educations or careers while facing the prospect of more than 60 years in prison. We hope the government continues to carefully examine the evidence it has against the remaining 59 defendants, at least some of whom we continue to believe are innocent.”

The decision to drop most of the cases came less than a month after a D.C. Superior Court jury found the first six protesters to face trial not guilty.

“The government will be filing motions to dismiss without prejudice the indictment against the other remaining 129 defendants so it can focus its efforts on this smaller, core group that we believe is most responsible for the destruction and violence that took place on Inauguration Day,” U.S. attorney spokesman Bill Miller said Thursday.

The notice of intent to proceed, filed with Superior Court Chief Judge Robert Morin on Thursday, says the government will go after people it claims organized the protests, intentionally used black bloc tactics or “engaged in identifiable acts of destruction, violence or other assaultive conduct.”

“The government will file individual motions to dismiss, without prejudice, the indictment against the remaining 129 defendants whose cases remain pending,” Assistant U.S. Attorney Jennifer Kerkhoff wrote in the notice. “In so doing, the court, the government and the 59 defendants can proceed more expeditiously with their trials.”

Prosecutors say the violent black bloc protesters did not have a permit when they gathered in Logan Circle on the day of Trump’s inauguration. They say the group moved 16 blocks through the streets, smashing windows and damaging other property before charging through a police line.

Police used flash-bang grenades to break up the crowd blocks from the White House, where demonstrators set a limousine on fire and threw rocks and other objects while peaceful protesters shouted slogans and carried signs condemning the newly sworn-in president.