An Istanbul court is expected Tuesday to deliver a "landmark" verdict on 16 civil society activists on trial for sedition.
For one of the defendants, a leading philanthropist and supporter of civil society, the case is drawing international scrutiny seen as pivotal in determining the direction of the country.
"The outcome of this case will show the rest of the world whether respect for human rights has any part to play in the Turkish justice system," Milena Buyum, Amnesty International's Turkey campaigner, said in a statement released Monday.
Prosecutors accused the 16 defendants of supporting and organizing anti-government protests in 2013 against then-Prime Minister Recep Tayyip Erdogan, who is now president.
The protests were called the Gezi movement after the park in Istanbul where they began. Prosecutors are calling for sentences of up to life in prison without parole.
Among the accused is Osman Kavala, one of Turkey's leading philanthropists and supporters of civil society, who has been jailed for more than two years.
"He has been a very key linchpin figure in civil society. That is why he has been targeted, and that's what the European court also said," said senior Turkey researcher Emma Sinclair-Webb of Human Rights Watch.
"The European court said in December in its ruling the prolonged arbitrary detention is politically motivated and has a chilling effect on the rest of civil society," she said.
Criticism from international observers
The European Convention on Human Rights (ECHR) called for Kavala's immediate release and an end to the case; however, the Istanbul court refused to release him, saying the ruling was being appealed.
The court had released the other 15 defendants at earlier hearings, but they all now risk being returned to jail.
"The prosecutor is asking for an aggravated life sentence based on accusations that pass as evidence in the indictment and with meaningless, incoherent, unreasonable interpretations," Yigit Aksakoglu, a child development specialist who is on trial with Kavala, said in an interview with Turkish media.
Aksakoglu spent seven months in solitary confinement before being released from pre-trial detention.
Along with the ECHR, international observers have also sharply criticized the prosecutor's case, claiming that no concrete evidence has been produced and that prosecutors relied mainly on the testimony of anonymous witnesses.
"There is nothing there to support such allegations and charges," said Sinclair-Webb. "It's a very example of the misuse of the criminal law, an unfair trial with politically motivated charges."
Controversy increased further at the last hearing in January with the judge's refusal to allow the cross-examination of prosecution witnesses.
Sinan Gokcen, the Turkish representative of Swedish-based Civil Rights Defenders, claims the case is part of a broader strategy by Ankara.
"Their arrests and this unlawful detention period and denial of all international procedural rights has had a huge effect on civil society. It's direct intimidation," Gokcen said.
Conspiracy vs. popular uprising
But Erdogan is vigorously defending the prosecution of the 16 defendants, insisting the Gezi protest was a carefully orchestrated nationwide conspiracy against his rule, organized and financed in part by Kavala and his network of supporters.
A few months before Kavala's prosecution, Erdogan labeled Kavala a public enemy, accusing him of "financing terrorists" and being a representative of "that famous Jew (George Soros), who tries to divide and tear up nations."
Erdogan did not elaborate on the comments about Soros, who is an international philanthropist.
Six years after the Gezi protests, Erdogan continues to portray the unrest as a conspiracy rather than a popular uprising. At its peak, Gezi spread to nearly every major city and town. Most observers say that rather than being a plot, Gezi was a grass-roots movement with no leadership and in reaction to Erdogan's increasing authoritarianism.
If Kavala and the 15 other defendants are convicted, Ankara could pay a high price. The EU has sharply criticized the case, criticism that has increased with the ECHR's condemnation of the trial.
Ankara is looking to the EU for financial support to deal with the latest refugee exodus from Syria's Idlib province. Analysts warn that assistance could be conditional.
"(German Chancellor Angela) Merkel vaguely promised new aid to Turkey for Syrian refugees," said analyst Atilla Yesilada of Global Source Partners. "But according to European Union Turkey rapporteur Nacho Sanchez Amor, if any aid is forthcoming, it will be conditional on the release of people like Osman Kavala and Selahattin Demirtas (the former leader of Turkey's pro-Kurdish HDP)."
Other analysts suggest Brussels' priority is to appease Erdogan, ensuring the Turkish president doesn't carry out his frequent threat to open the borders, which could potentially unleash a new wave of refugees into Europe.
For Aksakoglu, Tuesday's verdict is a matter of life or death.
"He (the prosecutor) wants me to spend my whole life without any hope of leaving the prison. This is equal to capital punishment in Turkey," he said.