By Ayla Jean Yackley
ISTANBUL (Reuters) - Twenty-six people went on trial in Istanbul on Thursday on charges related to organizing anti-government protests last year in a case that rights activists have described as a scandal.
The defendants join an estimated 5,500 people on trial in 95 separate prosecutions, including some on terrorism charges, according to Turkish rights groups, linked to the unrest that challenged Prime Minister Tayyip Erdogan's decade in power.
In the latest court case, five of the defendants are accused of forming a criminal organization - which they deny - and could face up to 30 years in prison, lawyers said.
The indictment cites, among its primary pieces of evidence, messages on social-media websites Twitter and Facebook that encouraged people to come to public protests.
"It is an absolutely scandalous prosecution that should have never been brought to court," Andrew Gardner, Turkey researcher for Amnesty International, said earlier this week.
"The indictment is completely without evidence of a crime, in the understanding of international human rights laws and Turkey's own laws ... The right to peaceful assembly is being put on trial," he told a news conference.
Most of the defendants are part of Taksim Solidarity, an ad hoc collection of engineers, architects, doctors, business owners and activists who opposed Erdogan's plans to redevelop Taksim Square, including razing Gezi Park to build a shopping center, amid a construction boom that has transformed Istanbul.
The small environmental movement to save Gezi, one of the few public green spaces in Europe's biggest city, quickly mushroomed into nationwide anti-government protests in June 2013, with many accusing Erdogan of authoritarianism.
At least six people died in clashes with police, and the Turkish Medical Association says 10,000 were seriously hurt.
"We came together as Taksim Solidarity to fulfill our duties and protect our most basic constitutional rights," architect Mucella Yapici, who is accused of leading the protests, told a packed courtroom, denying the charges against her. Yapici's daughter Cansu, 27, is also on trial.
Other defendants in the latest trial risk between one- and three-year jail terms for offences such as breaking the law on public assembly, according to the indictment.
Thousands of other defendants face charges mainly to do with violent incidents that occurred during the unrest.
Erdogan has depicted the protests as an international conspiracy and part of a failed coup d'etat attempt against his rule. He remains Turkey's most popular political figure and is widely expected to run for president in an August election.
"This trial is the government's effort to discredit the Gezi movement ... but the reality is: Taksim Solidarity awakened public opposition that was dormant since probably the 1980 (military) coup," said Melda Onur, an opposition lawmaker.
Erdogan's critics say the government is using courts to quash that political dissent, and some observers say the trials of Gezi activists have a chilling effect on civil society.
"There is no question that there is an atmosphere of intimidation and creation of a fear psychosis within society," said Amnesty's secretary-general, Salil Shetty.
Sporadic protests have hit Turkish cities over the past year, but their size has dwindled. On the May 31 anniversary of the start of the Gezi protest, a reported 25,000 police officers fired tear gas to disperse a crowd of about 1,000 people near Taksim trying to commemorate those who had died in the unrest.
The indictment said some protesters last year used bottles and rocks to repel police officers trying to clear Gezi Park, and that other groups built barricades in the road, threw Molotov cocktails and ballbearings and used percussion bombs.
Human Rights Watch drew attention to the failure to investigate most of the police who were accused of wrongdoing during the protests. "Just a handful of police have faced any kind of criminal prosecution for excessive use of force and their role in the deaths of three protesters," it said.
(Editing by Mark Heinrich)