Three people go on trial in Luxembourg on Tuesday over the so-called LuxLeaks scandal that exposed the country's huge tax breaks for major international companies, with the issue riding high after the recent Panama Papers revelations.
Two former employees at services firm PwC, Antoine Deltour and Raphael Halet, and journalist Edouard Perrin face charges over the leaking of thousands of documents that exposed the scandal.
The LuxLeaks affair erupted in November 2014, exposing deals that saved firms including Apple, IKEA and Pepsi billions of dollars in taxes while European Commission President Jean-Claude Juncker was Luxembourg's prime minister.
The deals emerged after a series of global news outlets examined 28,000 pages of documents obtained by the International Consortium of Investigative Journalists (ICIJ), revealing the full scale of the tax breaks won by 340 companies.
Former auditor Deltour is accused of stealing documents from the database of the accounting firm before he left in 2010, revealing business secrets, violation of professional secrets and money laundering.
The documents later became the basis of a story by Perrin on the state-owned France 2 TV station in 2012 but the story stayed under the international radar until the LuxLeaks document dump.
Perrin is charged with being an accomplice in all the offences, while Halet, accused of being behind a separate leak, faces the same charges as Deltour. All three of the accused are French.
Tax campaigners are expected to demonstrate outside the court in Luxembourg on Tuesday at the start of the hearing. The trial is expected to last until May 4.
Despite facing between five and 10 years in prison, Deltour insists he has no regrets.
"At first I was just an anonymous source, and then I found myself at the front of the stage," Deltour told AFP at his home in eastern France on the eve of the trial.
- Tax campaigners slam 'farce' -
LuxLeaks was the biggest expose of its kind until the Panama Papers this year revealed links between a number of international leaders to offshore shell companies that can be used to launder wealth.
Juncker faced huge pressure in his first weeks as Commission head after the revelations.
The two scandals have forced the EU to take tougher action against tax-avoiding companies, with ministers agreeing at the weekend on a fresh series of measures to fight such deals.
European Competition Commissioner Margrethe Vestager, who has launched tax inquiries into a number of firms including Amazon, has been invited to testify at the trial in Luxembourg.
"We are considering the answer," a Commission spokeswoman said on Monday.
The European Parliament came under fire recently for trying to push through a new law on the protection of trade secrets which critics say will make it easier to prosecute whistleblowers.
The Commission said there were a "number of protections" for whistleblowers.
Aid group Oxfam, which has campaigned for a crackdown on tax avoidance, said the LuxLeaks defendants should be "celebrated and not prosecuted".
"It's only through the courageous actions of individuals like Antoine Deltour that the public is alerted to tax abuse, which costs countries -- including very poor ones -- billions of dollars every year," said Max Lawson, an Oxfam spokesman.
Activist group Eurodad said the men on trial in Luxembourg were "heroes".
"The court case against them is a farce. They acted in the public interest, and deserve protection from prosecution," Eurodad's tax coordinator Tove Maria Ryding said.