Thousands of supporters filled the streets outside a court in Barcelona on Monday as the former Catalan president Artur Mas went on trial.
He is accused of serious civil disobedience over Catalonia’s unofficial vote in November 2014 seeking independence from Spain.
The vote went ahead in defiance of an order from Spain’s constitutional court.
Prosecutors are calling for him to be disqualified from office for 10 years.
Mr Mas, his deputy Joana Ortega, and Catalan former education minister Irene Rigau face accusations ranging from disobedience and perverting the course of justice to misuse of public funds.
Large crowds appeared outside the court in Barcelona on Monday chanting “you are not alone”, “democracy is not a crime” and “independence”.
The case is being used by pro-independence supporters to galvanise their campaign. The current government has promised to hold a new vote in September.
The 9 November 2014 vote, which was not binding, went ahead despite vehement opposition from the national government and it was outlawed by Spain’s constitutional court.
Catalan officials say more than 80% of those who voted backed independence. However, only two million voters out of an estimated 5.4 million who were eligible took part.
On Sunday, Mr Mas told a news conference in Barcelona that the Catalan government was “determined to go forward”.
“We did what had to be done in 2014 and we would do it again if the circumstances allow it,” he said.
Current Catalan President Carles Puigdemont said the countdown had begun for an independent Spanish state in Catalonia.
Like other regions in Spain, Catalonia already has the power to run its educational and healthcare systems, as well as limited freedoms in the area of taxation.
Catalonia is one of Spain’s richest and most highly industrialised regions, and also one of the most independent-minded.
With a distinct history stretching back to the early Middle Ages, many Catalans think of themselves as a separate nation from the rest of Spain.
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