Twelve Catalan separatist leaders arrived at the Supreme Court early Tuesday as the full weight of Spain's political expectations as well as the country’s international reputation fell on the judiciary who have somehow to chart a way to a verdict likely to have many very vocal detractors as well as backers.

The defendants face serious charges after having held an illegal regional referendum that led them to trigger a bid to secede unilaterally from the rest of Spain, acts that went against the country's constitution as well as numerous court rulings.

Somehow the judges at the court will have to deliver a verdict that does not raise accusations that the trial was a hangover from Spain's hard-line authoritarian past while at the same time satisfying domestic demands for justice by Spaniards who consider their constitution as the very glue that binds their historically divisive land together.

"Spain can change its constitution," said Quim Torra, president to the regional government of Catalonia. "An independent republic is still our goal. We also want the freedom of the prisoners because they are innocent," he added.

Torra was seen arriving at the court, where a seat had been reserved for him to observe proceedings.

The court had on Feb. 1 ruled that it was not going to give accreditations to national or international observers because all proceedings would be televised and made available on live streaming.

The streaming began at 10.00 am but crashed when what the court described as more than 40 “malicious requests” per second hit the system.

Broadcasts were resumed when the problem was fixed, the court said.

The case opened with defense lawyers questioning the impartiality of the court and stressing that the fundamental rights of their clients had been violated.

The disquiet that the separatists have awakened in Spain was visible on Sunday when Madrid's central Colon Square filled with around 45,000 protesters who chanted that the referendum and attempted declaration of independence were nothing short of a coup attempt against the government of Spain.

One protagonist of the separatist bid that was absent at the court was Carles Puigdemont, the regional government’s president at the time of the referendum and the person who announced the declaration of independence.

Rather than run the risk of arrest, Puigdemont fled into exile in Belgium.

As the trial began he was in Berlin where he told reporters that the Spanish state still had in this trial an opportunity to "rectify" and said the only fair verdict would be "acquittal."

“If we came to organize a referendum on October 1 (2017) it was because our requests to hold a ballot agreed with the central government were rejected,” he said.

From Scotland, Nicola Sturgeon – the leader of the regional government and the Scottish National Party – said the future of Catalonia should be decided through democracy and not in the courts.

“These trials of elected politicians should concern all democrats,” she said on her official Twitter account. “Let’s hope the process is demonstrably fair,” she added.

A referendum on Scottish independence from the United Kingdom took place in Sept. 2014, though on that occasion, the vote had been legally agreed with the government of the UK and voters chose with a majority of more than 55 percent to remain linked to the rest of the kingdom.

Alex Salmond, the SNP leader who campaigned for Scottish independence and lost the referendum, told Catalan regional TV3 that it had taken his country 60 years to secure such a ballot.

The European Commission said it trusted in Spain’s judiciary and did not want to politicize the situation.

"We fully trust the legal system of Spain and the most important thing is to make sure everything happens in accordance with the Spanish Constitution," Jyrki Katainen, the EC's Vice-President for Jobs, Growth, Investment and Competitiveness, said.

"For us, it is not a political issue, we do not want to make comments or political statements about developments," he added.

Some 15 European Parliament lawmakers belonging to the EU-Catalonia Dialogue Platform, a support group for the independence movement based in Brussels, said the trial was not just a Spanish internal affair.

"This trial is not an internal Spanish issue, it has a clear political dimension," they said in a statement that went on to argue that the "criminal accusation" at its core should be abandoned "to make way for dialogue."

Some protesters who were clearly nostalgic for Spain's hard-right dictatorship under Gen. Francisco Franco were seen carrying fascist symbols outside the court as proceedings got underway inside.

Roads were cut early Tuesday in Madrid to allow police vans carrying the suspects' easy access to the court while 3-kilometer (1.8-mile) traffic jams formed in rush-hour Barcelona as protesters angry with the beginning of what they consider to be a political show trial blocked some of Catalonia's main highways and traffic arteries.

One of the key elements to be weighed up by the judges is whether violence was used in the secessionist bid.

Prosecutors are set to argue that the defendants triggered citizen pressure as an "intimidating force" in Catalonia and that there was also an outbreak of violence near a regional government building while secession was being plotted.

"The images of October 1 clearly show that the violent actions came only from the Spanish riot police and not from Catalan voters or from the politicians who performed the referendum," Torra said.

The charges brought against the defendants include rebellion, sedition and the misuse of public funds, and if the judges' verdicts opt for the harshest punishments, some of the separatists could be jailed for 25 years, having already spent one in pre-trial detention.

By Harold Heckle