TENS of thousands of demonstrators from across Catalonia are expected to gather in the Spanish capital of Madrid for a rally against the trial of pro-independence leaders.

More than 500 coaches have been booked for this evening’s gathering, which is being held under the banner: “Self-determination is not a crime. Democracy is to decide.”

It has been organised by grassroots groups the Catalan National Assembly (ANC) and Omnium Cultural, whose heads are among those on trial, and pro-independence parties in the Catalan Parliament.

President Quim Torra is expected to attend, along with a number of his ministers, around half of Catalonia’s MPs, and representatives from other civic and social groups.

Organisers are hoping to attract more than 45,000 people. That’s the number of people who attended a previous rally by right-wing demonstrators who opposed Spanish government dialogue with Catalonia.

“With this demonstration, we want to denounce the persecution and prosecution of political dissidents in Spain,” said the ANC. “Self-determination is a democratic right included in several international treaties that Spain signed and ratified ... Democracy itself is on trial and we cannot let this happen.”

The march comes after defence teams complained at presiding judge Manuel Marchena’s indication that there will be no audio-visual evidence at this stage of the trial, which has just ended its fourth week.

Civil Guard and National Police officers are expected to appear in coming weeks with a focus on the level of violence they used to try to stop the October 2017 independence referendum. The lawyers said audio-visual evidence would be “indispensable” should the officers’ evidence

contradict the images.

They base their complaint on the Spanish constitution and the European Convention on Human Rights, and are invoking a precedent signed by Marchena, which stated that when there was an obvious contradiction between a witness account and documentary evidence, the accused have the right to counteract the contradictions.

In another development, an Austrian newspaper has said the candidacies of ex-Catalan president Carles Puigdemont and his former deputy Oriol Junqueras in the European Parliament elections made the issue of Catalonia a European one.

Der Standard said it is “an internationalisation of the conflict”, and forecast a revival of tensions between Catalan pro-indy parties and the Socialist government of Pedro Sanchez.

“They voted against the budget of Pedro Sanchez after he refused to open dialogue on a future independence referendum,” it said. “This scenario could be repeated ... he will need the votes of ... Podemos-IU and ... the Basque and Catalan parties to obtain a majority. If that’s what happens, the self-determination question will be on the table again.”