Three pro-independence politicians in Catalonia go on trial on Monday for defying the justice system, amid mounting legal tensions surrounding their region’s plan to break away from Spain via a referendum later this year.

Artur Mas is accused of disobeying court orders and perverting the course of justice by holding a non-binding ballot on Catalan independence in 2014, when he was regional premier. Two of his former colleagues, Joana Ortega and Irene Rigau, will also be tried for their role in organising the vote. They could be barred from public office for nine years if found guilty. Mas, seen as the instigator of the current independence drive, could be barred for 10 years.

The so-called “consultative process” of 2014 saw more than two million Catalans vote. More than three-quarters of them favoured independence, although the vast majority of unionists stayed away due to the illegal nature of the ballot. Polls currently suggest Catalans are split down the middle on independence.

Tens of thousands of independence supporters are expected to turn out on Monday at the Barcelona court where the trial will take place. Claiming that Madrid is making overly aggressive use of the judiciary to thwart the secessionist process, the demonstrators’ slogan is: “On February 6th, we’re all on trial.”

“This is not a trial that has a legal basis,” Mr Mas said last week. “It’s a trial initiated by the state attorney, not by Catalan attorneys, in connivance with the Spanish government of the Popular Party.”

Binding referendum

Mr Mas’s successor as Catalan premier, Carles Puigdemont, plans to hold a binding referendum on independence later this year. He and the regional government, led by the Junts pel Sí (Together for Yes) coalition, say they want to negotiate the terms of a Scotland-style vote with Madrid. However, with conservative prime minister Mariano Rajoy adamant that that will not happen, Mr Puigdemont says the referendum will take place anyway.

The ongoing standoff between Barcelona and Madrid has been based on the separatists’ claim that self-determination is a democratic right, while the Spanish government says the constitution contains no such provision.

In recent months, the Spanish administration has appeared to make some moves to reach out to the northeastern region in a bid to calm tensions, a strategy widely dubbed “Operation Dialogue”. The media-friendly deputy prime minister, Soraya Sáenz de Santamaría, has led the initiative, setting up an office in Barcelona and promising to examine Catalan grievances.

But the trial beginning today is expected to deepen the independence camp’s sense of victimhood, and in the past few days, instead of cooling, the war of words has escalated. Last Wednesday, Mr Puigdemont reiterated his plan to stage the referendum, but with the added detail that it might happen before September, as had previously been scheduled.

His comments came just days after the Catalan parliament ended months of uncertainty by approving the 2017 regional budget. The backing in that vote of the anti-capitalist Popular Unity Candidacy (CUP), whose political support keeps the independence project alive, is believed to have stiffened Mr Puigdemont’s resolve to stage the referendum.

‘Very radical model’

Ms Sáenz de Santamaría has warned that the secessionist movement’s “very radical model” is stifling genuine debate. Justice minister Rafael Catalá, meanwhile, has suggested that Madrid might trigger an article in the constitution allowing the central government to suspend the autonomous powers of any renegade region. This, for example, would allow the Spanish government to take control of Catalan schools that might have been used as voting posts in the planned referendum.

A series of police raids on Thursday further fuelled the antagonism. The civil guard arrested 18 people during searches of several properties, mainly in Barcelona, as part of an investigation into the alleged illegal financing of Convergència, the party of Mr Mas and Mr Puigdemont before it was rebranded and renamed in 2015. Several of those investigated are close to Mr Mas, who dismissed the raids as a politically driven “set-up” to undermine the independence movement.

However, a very different interpretation from the secessionist side came from María José Lecha, of the CUP, who warned that the arrests were “a tremendous blow for the independence process, which has to be squeaky-clean”.

Meanwhile, a group of around 30 renowned Catalan jurists has entered the fray, publishing a manifesto in which they call on the region’s people to respect the rule of law and not to heed secessionist calls “to breach or infringe upon the current legal framework”.