Police officers "knocked down" a 10-year-old boy and exposed him and his mother to pepper spray during a rally against US President Donald Trump's inauguration, according to amendments to a lawsuit filed by a civil rights organisation.

The lawsuit, which was originally filed by the American Civil Liberties Union of the District of Columbia (ACLU-DC) on behalf of four plaintiffs in June, was amended on Wednesday to add the 10-year-old boy and his mother, Gwen Frisbie-Fulton.

The lawsuit names the child as "A.S." in order to protect his identity.

During Trump's inauguration on January 20, 2016, protesters from across the country amassed in the nation's capital.

When police kettled a group of demonstrators, bystanders, journalists, medics and others who had been present during an anti-fascist and anti-capitalist bloc march, the officers continued to use pepper spray and other weapons, such as stinger grenades, against them.

Frisbie-Fulton and A.S., who had been nearby, were caught in the mayhem, according to the lawsuit.

"As she and A.S. tried to escape the spraying, a line of officers knocked A.S. to the ground. Frisbie-Fulton picked A.S. up and tried to carry him away from the melee, but she coughed and choked from the thick clouds of pepper spray, and could not carry him further," the ACLU-DC's statement explained.

Frisbie-Fulton claimed the officers endangered her and her son's safety.

"I was terrified for my son's safety. When he was knocked down, I instinctually jumped on top of him to cover his body with mine," said Frisbie-Fulton, as quoted in the press release.

"We are told the police are there to keep us safe, but on Inauguration Day they were the ones who put us in danger."

Speaking to Al Jazeera by telephone, Scott Michelman, senior staff attorney at the ACLU-DC, said the addition of Frisbie-Fulton and her son to the lawsuit "reveals the extent of the police department's wantonness on Inauguration Day".

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"There is no argument that the 10-year-old peaceful protester or his mother were part of any riot or posed any threat," Michelman said, arguing that the incident further demonstrated that "the police were out of control that day".

The MPD declined Al Jazeera's request to comment.

The complaint's amendments also identified 27 Metropolitan Police Department (MPD) officers, among them eight supervisors, who the ACLU-DC alleges ordered or engaged in unlawful police conduct, the rights group's statement added.

When the lawsuit was first filed on June 21, the only named defendant was Police Chief Peter Newsham.

"We were pleased to be able to name these specific officers," said Michelman, explaining that the identification of the individuals was possible through a combination of witness accounts, plaintiffs' recollection, photographs and testimony.

"Unlike the US Attorney's Office, which charged over 200 people criminally based on the actions of a few, we tried very hard to only name people we have reason to believe personally did something wrong, either by using excessive force or ordering some of the constitutional violations we allege."

'Molestation and rape'

The lawsuit was initially filed on behalf of four plaintiffs - two demonstrators, a photojournalist and a legal observer - all of whom alleged unnecessary force and police brutality while in police custody on Inauguration Day.

One of the plaintiffs, journalist Shay Horse, said in the complaint that he "felt like they were using molestation and rape as punishment" when he was subjected to aggressive rectum examinations.

"It felt like they were trying to break me and the others - break us so that even if the charges didn't stick, that night would be our punishment," Horse said.

Horse and the other three original plaintiffs were among more than 230 people who were surrounded, rounded up and arrested during the anti-capitalist and anti-fascist bloc rally.

The protesters have been accused of engaging in property damage.

Most of those arrested were later issued a felony rioting charge that carried a maximum penalty of 10 years in prison and a $25,000 fine.

On April 27, the DC Superior Court returned a superseding indictment that issued a slew of felony charges to 212 defendants, three of whom were not present in the initial batch of those charged.

Two of the plaintiffs represented by the ACLU-DC are currently among those charged by the DC US Attorney's Office.

Last month, a jury found the first group of six defendants, among them independent journalist Alexei Wood, not-guilty on all counts.

Some of those charges have been dropped and others lessened, but 188 people - known collectively as the "J20 defendants" - are still facing charges that could carry heavy penalties.

While at least six of the remaining defendants have had their charges reduced to misdemeanours, the bulk remain accused of felony charges that could land them behind bars for more than six decades.

'Politically motivated'

Sam Menefee-Libey of the DC Legal Posse, a group that supports the Inauguration Day Defendants, described the charges as "politically motivated".

"The riot charge itself is a criminalisation of collective action," he told Al Jazeera.

Along with witnesses and defendants, several rights groups and watchdogs have accused the MPD of police brutality and unnecessary force.

The Washington, DC, City Council paid a consultant group, The Police Foundation, to investigate police conduct during the Inauguration Day protests.

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That move has been blasted by critics who claim The Police Foundation has a history of bias in favour of police accused of wrongdoing.

The ACLU-DC's Michelman added: "The police's responsibility is to act with restraint, to respond to only instances where they have probable cause particular individuals broke the law and to not conduct mass roundups or use chemical weapons indiscriminately."