Spain’s supreme court is expected to announce its verdict on Monday in the trial of 12 Catalan separatist leaders over their alleged roles in the region’s failed attempt for independence two years ago.

Nine of the defendants – who include the former Catalan vice-president Oriol Junqueras, the former speaker of the Catalan parliament Carme Forcadell, and two influential grassroots activists, Jordi Cuixart and Jordi Sànchez – are accused of rebellion, which carries a prison sentence of up to 25 years. Other charges include sedition and the misuse of public funds.

The unilateral independence referendum, held in defiance of the Spanish constitution on 1 October 2017, provoked Spain’s biggest political crisis since its return to democracy after the end of the Franco dictatorship.

Less than a month after the poll, which was met with a heavy-handed police response, the Catalan parliament made a unilateral declaration of independence.

The Spanish government reacted to the move by using the constitution to assume direct control of the region and sack the pro-independence regional president Carles Puigdemont and his administration.

The trial, which has been held at the supreme court in Madrid, lasted four months and heard from more than 400 witnesses, including Spain’s prime minister at the time of the referendum, Mariano Rajoy.

The proceedings also examined the events of 20 September 2017, when police raided Catalan regional government offices and arrested 14 senior officials in an attempt to head off the vote.

The raids brought thousands of Catalans out to protest. Guardia Civil officers found themselves trapped inside the buildings they were searching and three of their vehicles were vandalised.

Javier Zaragoza, prosecuting, argued such behaviour by the protesters constituted “physical, compulsive and intimidatory violence”, adding: “The violent nature of an uprising does not mean there has to be either serious or armed violence.”

Zaragoza told the court that the push for secession had been a coup d’état designed to “overturn, suspend the constitution completely or partially, and declare the independence of one part of the national territory”.

However, defence lawyers rejected such arguments, telling the court that while there may have been “disobedience”, there had been no rebellion.

The supreme court has refused to comment on reports that the trial judges have decided to acquit the defendants of the most serious charge of rebellion, which involves “revolting violently and publicly”.

Under the Spanish penal code, the lesser offence of sedition is defined as “rising up publicly and tumultuously to prevent, through force or beyond legal means, the application of the law”. It carries a maximum prison sentence of 15 years.

Puigdemont is not among those on trial. He fled into self-imposed exile in Belgium to avoid arrest.