ISTANBUL — A well-known Turkish philanthropist went on trial again in Istanbul on Friday, his third prosecution in four years of detention, in a mass proceeding that has come to demonstrate the extreme lengths the Turkish government is willing to take to keep its opponents behind bars.
In a highly contested move, prosecutors merged the cases against three groups of defendants, most of whom have already been acquitted of any charges, to establish a new case against 52 people. The philanthropist, Osman Kavala, is the best known among the group, which includes football fans, environmentalists and artists who took part in the Taksim Square protests of 2013.
Mr. Kavala made a statement by video link from Silivri Prison, outside Istanbul, where he has been held mostly in solitary confinement for the past four years. A panel of judges ordered him to be further remanded in custody.
Charged with trying to overthrow the government and undermine the Constitution by violence, all of the defendants have long insisted they are innocent. The group also includes an American academic, Henry Barkey, who is accused of being in touch with Mr. Kavala at the time of an attempted coup in 2016. Mr. Barkey has denied any involvement in the event.
Amnesty International described the merging of the cases as “farcical” and a “shocking disregard for fair trial procedures.”
For President Recep Tayyip Erdogan, the Taksim Square protests, a peaceful movement meant to save a park from being replaced by a shopping mall, have come to represent the first of a series of challenges to his leadership. The demonstrations spread across the country and were for many youthful activists a formative event, before the police moved in and forcibly crushed them.
Yet Mr. Erdogan often refers to the Gezi protests, as they are known in Turkey after the name of the park, as the first coup attempt against him. Under this narrative, anticorruption raids against his officials later that year, and the coup attempt against him in July 2016, were a continuation of foreign-inspired, violent efforts to overthrow his government.
His unrelenting pursuit of those involved in the protests, and in particular with Mr. Kavala, so many years later has, however, mystified many since Mr. Kavala was not a political figure and his philanthropy work focused on earthquake reconstruction and cultural and artistic programs for minorities.
Mr. Kavala was arrested in 2017, and charged and later acquitted of orchestrating and financing the protests by channeling money from the billionaire investor George Soros to the protesters, as well as participating in the 2016 coup attempt. After his acquittal, he was charged with espionage based on the same evidence. (Mr. Erdogan has accused Mr. Soros of supporting Mr. Kavala in financing “terrorists” during the protests.)
“This case almost seems to be a vendetta at this point,” said Asli Aydintasbas, a senior fellow at the European Council on Foreign Relations. “What Osman has been going through is irrational and unnecessarily cruel.”
In his statement to the court, Mr. Kavala said the twists and turns in his prosecution were an indication of political interference aimed at prolonging his imprisonment. The purpose, he said, was to keep alive the perception of his guilt and to criminalize the Gezi protests as an act of rebellion, “although the evidence points to the contrary.”
“What is striking about the charges brought against me is not merely the fact that they are not based on any evidence,” he said. “They are allegations of a fantastic nature based on conspiracy theories overstepping the bounds of reason.”
Other defendants raised similar complaints.
“I have been tried twice under the same indictment,” said one, Mucella Yapici, a leading member of the Taksim Solidarity movement, which was formed at the time of the protests. “I was acquitted, and my acquittal was approved. Twice. I reject this case, by reason, ethics and conscience,” she said in court in comments a support group relayed on Twitter.
A panel of three judges rejected lawyers’ requests to separate the three cases, leading one group of lawyers to walk out.
“Here, the referee of the game is trying to score a goal,” said Riza Kocal, a lawyer for the defendants belonging to Carsi, a fan group of the Besiktas football club in Istanbul. “The joining of cases is baseless. Each file should be sent to its own court.”
Even as Mr. Erdogan, who faces increasingly severe economic and political challenges at home, has sought to repair relations with the United States and Europe, he has repeatedly rejected calls to improve Turkey’s poor record on justice or to release prominent political prisoners like Mr. Kavala.
Turkey has ignored several decisions by the European Court of Human Rights pressing for the release of detainees like Mr. Kavala. That has prompted human rights organizations to urge the committee of ministers who oversee the court to begin infringement proceedings against Turkey, a rare action that could lead to its suspension from the court.
“The Turkish courts and prosecutors have engaged in a series of tactics to circumvent the authority of the E.C.H.R. and the Council of Europe,” Aisling Reidy, senior legal adviser at Human Rights Watch, said in a statement at the time. “They have issued repeated sham release orders, initiated multiple criminal proceedings on the same facts, repeatedly issued detention decisions while adopting unwarranted procedural decisions to prolong detention.”
The Kavala affair has done a lot of damage to Turkey’s standing in the United States Congress and across Europe, Ms. Aydintasbas said. “A rational actor would have let Kavala go long ago, knowing that would buy Turkey some good will at the lowest point of its relations with the West.”
“I think at this point it’s more of a systemic obsession than anything else,” she added. “Everyone knows Osman, as a civil society member, is not a political threat to anyone. He didn’t organize Gezi or the coup and I doubt anyone actually believes that.”
The next hearing will be on Nov. 26, the judge said.