Hervé Falciani, a 43-year-old French-Italian national, leaked a cache of documents allegedly indicating that HSB C's Geneva private banking arm helped more than 120,000 clients to hide €180.6 billion ($205.4 billion) from tax authorities.
While he is widely viewed as a whistleblower and hailed as a hero in countries where his leaked information is helping to net tax cheats, the Swiss authorities remain intent on prosecuting him.
"I am not going," Falciani told reporters in Divonne-les-Bains, France, just a stone's throw from the border with Switzerland where he is facing charges of data theft, industrial espionage, and violating the country's long-cherished banking secrecy laws.
"In Switzerland, the conditions for a fair and balanced trial are not there, in my opinion," he said.
Falciani failed to show for his trial in the southern Swiss city of Bellinzona earlier this month, and his case was adjourned until November 2nd.
As a French national living in France, he cannot be extradited to Switzerland.
But under Swiss law, the trial may continue without him if he fails to show up when the proceedings resume next month.
Falciani, who has been offered a safe-passage to attend his trial in Switzerland, said he believed he could secure a lighter sentence if he did so, but that he did not want to take the "easy way out".
Pressure from bank?
He said he thought HSBC was pressuring the Swiss authorities to move ahead with the trial in a bid to "rescue the appearance of respectability" of some financial actors.
Geneva prosecutors in June closed their investigation into HSBC's alleged wrongdoings after the bank agreed to pay tens of millions of dollars in compensation.
Geneva lead prosecutor Yves Bertossa at the time explained that the authorities preferred to reach a negotiated solution with HSBC because of the difficulties in proving money laundering.
"This trial comes at the behest of a bank that put money on the table to avoid being tried itself," Falciani charged Wednesday.
Falciani became an IT worker for HSBC in 2000 and moved to the bank's offices in Geneva in 2006.
The so-called "Snowden of tax evasion" and "the man who terrifies the rich" obtained access to a massive database of encrypted customer information, which was passed on to European fiscal authorities.
Falciani has rejected accusations that he was only seeking financial gain, insisting he had wanted to expose how banks support tax evasion and money laundering.
Though he remains wanted on data theft charges, France and Spain have offered him protection by refusing to extradite him to Switzerland.
Falciani spent a couple months in a Spanish prison in 2012 at Switzerland's request before winning release for helping Spain track down its tax cheats.