Artur Mas defied an order from the Spanish Constitutional Court by organising a non-binding referendum in 2014 in which the vast majority of Catalan participants voted for independence.
The former leader of Spain's Catalonia region, Artur Mas, will stand trial on Monday. He faces accusations of "serious civil disobedience" and "malfeasance" over an independence referendum he organised in November 2014.
The trial threatens to drive a wedge between the Spanish government in Madrid and some 2.3 million people who participated in the referendum, 80 percent of whom voted for independence.
TRT World spoke with Tim Parfitt, who has been following the story from Barcelona.
Thousands of supporters of independence for the wealthy, northeastern region gathered on the large avenue next to the Barcelona court on Monday morning.
Inside, Mas -- who was president of the semi-autonomous region from 2010 to 2016 -- will stand trial alongside his former vice president Joana Ortega and Irene Rigau, the official once responsible for education in Catalonia.
Prosecutors want them banned from holding public office for nine to 10 years for ignoring a ban on the referendum issued by the Spanish Constitutional Court.
Although the referendum was non-binding, a coalition of Catalan separatist parties that won regional elections in 2015 promise to steer the region towards a "real referendum" in September, with or without Madrid's consent.
According to a recent poll conducted by a Catalan public institute, 44.9 percent of Catalans want independence while 45.1 percent don't. A large majority, however, wants a referendum.