There is no formal deadline for the Supreme Court's seven judges to render a verdict, but a ruling is expected before November. By then the defenders will be spending two years in prison, after being denied in 2017.

The case has been closely followed by Spain, like the Basque region, which has its own separatist history. "Said Idoia Elorza, a Basque Nationalist Party official who traveled to Madrid this week with some colleagues to follow the trial's closing days.

The trial's most divisive issue has been the independence drive involved. On Wednesday, Jordi Turull, a member of the Catalan Government, said it was "an insult to the Catalan society" to suggest that a few leaders had handled more than 2 million voters in the October 2017 referendum. "Catalans are not sheep," he told the courtroom.

Other defenders also argue that the independence movement will continue to grow – with or without their help – and ultimately force the Spanish government to allow an independence referendum in Catalonia.

"The ballot box can not be threatened with democracy," said Jordi Sanchez, defending who faces up to 17 years in prison if convicted. "In Catalonia, there will be a ballot boxes and votes and we will have them as an agreement with the Spanish government, like in Scotland or Quebec."

If convicted, the defendants could appeal to the European Court of Human Rights, or they could be pardoned by Mr. Sánchez. However, Spain's Prime Minister is under stress to make further concessions to separatist politicians, highly following his unsuccessful effort to reopen a political dialogue with them last year. The talks went nowhere, and instead of the separatists, the vote goes down Mr. Sánchez's budget in February, forcing him into a snap election.

The defendants' closing statements, which referred to philosophical writings from Socrates to Hannah Arendt, also warned the judges directly that their ruling could significantly impact Spain's political future. "You have the responsibility of not worsening a political situation," Jordi Sanchez told the judges. "I would not like to be in your shoes now."