Hervé Falciani, wanted in Switzerland on allegations of stealing data on tens of thousands of Swiss bank accounts, appears before the High Court on April 15, 2013. REUTERS

Why did you come to Spain if you knew that there was an international arrest warrant for you?

“Because my life was in danger. Shortly before, the United States had warned me that it would be easy for someone to pay somebody to try to kill me. And I chose Spain knowing that I would go to jail and that Switzerland would request my extradition. My escape has been planned to the millimeter; this isn’t a casual coincidence.”

Forty-year-old Hervé Falciani motions with his thumb from one side of his throat to the other to highlight the fact that he runs the risk of being killed. The French-Italian former employee of the Hong Kong Shanghai Bank Corporation (HSBC) in Geneva has removed the bushy wig and black-rimmed glasses that he used to disguise himself when he appeared for an extradition hearing last Monday. Switzerland is demanding that the Spanish authorities turn him over. Now two days have passed since the hearing and Falciani has reverted to looking like himself — slightly alterd thanks to a goatee.

Falciani’s interview with EL PAÍS — the first with a Spanish media outlet — took place at a secret location. The High Court released him in December after he was detained trying to enter Spain through Barcelona last summer, and he is now a protected witness cooperating with anticorruption prosecutors who are investigating Spanish tax evaders.

Falciani has powerful enemies. Among them: HSBC, the world’s fourth largest bank in terms of market value, from which he stole lists from 2006 to 2008 of about 130,000 clients; the Swiss financial system, which has been religiously protective of its bank secrecy laws; and thousands of tax evaders who have been charged since 2009; some with ties to major drug cartels, organized crime groups and terrorist organizations.

What was the risk that Washington alerted you about?

“On June 1, 2012 — one month before I came to Spain — I started to work with US Justice officials in Paris. The Americans warned me that the US Senate would be launching serious allegations against HSBC because of its lax money laundering and terrorist financing controls, and that the bank would be prosecuted. I was told that from then on my life would be in danger. I had two choices: start a new life in the United States or travel elsewhere to buy some time. I was told that the only safe place in Europe would be Spain, which had successfully used my information in important cases like that of the Botín family. They believed that there was little chance that Spain would be likely to approve my extradition. In that way I could continue to work with Justice officials.”

Falciani said that feelers were put out to Spanish authorities to weigh up how they would react, but he declined to say who exactly was contacted.

On July 1, 2012 Falciani was arrested at the seaport in Barcelona after arriving on board a boat from Sète, France. Up until now, it was believed that his arrest on an international warrant issued by the Bern government was business as usual. Police sources had said that officers discovered his identity following a routine check of his travel documents.

His flight from France remained a mystery. Falciani had taken refuge at his home in Castellar, the last village on the French Riviera before the Italian border. On December 21, 2008 he fled Geneva for Italy and, until last summer when he came to Spain, he had been traveling safely between the two countries because he is a dual national and neither Italy nor France extradite their citizens.

Falciani said that traveling by boat, instead of automobile or train, was the best and safest option. Because he left by sea, immigration authorities in Sète asked for his passport and by the time he reached Barcelona, Spanish officials were waiting for him.

“In prison I was safe,” the former banker said. “The Americans initially proposed two dates for travel: July 1 or 3 of last year. They knew which judge they would call upon my arrival, and what would be more conducive for our strategy. On this basis, it was decided I should leave for Spain.”

Swiss officials have accused him of trying to profit from selling the client database after he appeared at the Beirut offices of Audi bank in 2008 using the pseudonym Ruben Al-Chidiak. “I’ve never asked anything of them; I only tried to help justice,” he said. “I’m sick of hearing fabrications coming from Switzerland.”

Falciani said he is now helping Spanish anticorruption prosecutors chase down the intermediaries — the people who help Swiss banks attract customers in Spain, France, Italy and Germany. Throughout his ordeal he has been separated from his wife and son. But he does plan on settling down to a peaceful life in the United States. “Americans can help us in this fight, but we cannot leave all this work in their hands. France, Spain and Europe in general: they also have to fight this war because it is the ordinary people who are suffering the consequences.”