A former security aide to French President Emmanuel Macron went on trial on Monday on a dozen charges, including voluntary violence, illegally wearing a police badge and carrying a weapon.
Alexandre Benalla, 30, sparked a political crisis when he was identified as having beaten up a protester during a May Day demonstration in 2018.
Mr Benalla faces up to seven years in prison and €100,000 ($118,000) in fines if found guilty.
His actions, and the handling of them by Mr Macron’s office, caused the French leader’s first major presidential crisis and discredited his efforts to clean up politics.
At the heart of the controversy was Mr Benalla’s murky role at the Elysee Palace, where a police security contingent has the job of protecting the president, and whether the presidency had a side deal with him.
Intense media coverage and a televised parliamentary inquiry that put top Elysee officials at centre stage turned the affair into a political soap opera.
Questions raised include why the aide stepped into the role of a police officer in the May Day confrontation as real police stood by watching. Mr Benalla was reportedly at the demonstration as an observer.
Among other questions was why he held two diplomatic passports, used for travel to African countries, after being dismissed from his ill-defined job at the presidential palace.
Another investigation was opened when a photo showed Mr Benalla with a gun at his hip while serving as a security aide for Mr Macron during his presidential campaign in 2017.
He faces a possible seven-year jail sentence for carrying a firearm.
Taking the stand on Monday, Mr Benalla spoke of being “surprised” by his arrest.
“I felt like I had done something positive for society by arresting delinquents," he said. "And I was taken into police custody.”
Mr Benalla is being tried with three others, two of them police officers who shared with him video-surveillance images of him striking a demonstrator. The tip-off is a breach of professional secrets.
Hundreds of violent demonstrators invaded the traditional May 1 march by unions when he moved into action in a small Left Bank square.
“It was war,’’ Mr Benalla told investigators, insisting that as an observer he had no intention of acting violently but intervened because it was his duty as a citizen.
He was initially given a 15-day suspension from his job before returning to lead security for the French football team’s victory parade down the Champs-Elysees Avenue on Bastille Day after winning the 2018 World Cup.
He was placed under investigation later in July and, amid public outcry, fired from his job at the presidential palace.