ZURICH (Reuters) - Switzerland's highest court has rejected a French request for help in investigating a married couple for tax offences, ruling that data stolen from HSBC's Geneva private bank was inadmissible.
The ruling comes amid the latest scandal to hit Credit Suisse after an anonymous tipster alerted Dutch authorities to thousands of suspect accounts that triggered police raids last week.
The French couple were discovered via information leaked by Herve Falciani, a former IT employee who fled HSBC in 2008 with files that he alleged showed evidence of tax evasion by clients.
The French newspaper Le Monde has said it identified more than 106,000 clients.
French officials asked Swiss tax authorities in 2014 for assistance in investigating the French couple suspected of having an undeclared bank account in Switzerland.
The Swiss authorities agreed, but their decision was overturned after an appeal by the unnamed couple.
In a March ruling announced on Wednesday, the Swiss Federal Supreme Court confirmed the lower court's decision. It said requests for administrative assistance would not be approved when based on information obtained illegally.
"The criminal origin of the Falciani data is undisputed," the court said in a statement. "Especially because Herve Falciani was convicted in 2015."
A Swiss court sentenced Falciani to five years in prison for aggravated industrial sabotage, but he has avoided serving time by remaining in France.
Falciani, a French citizen, has said he is a whistleblower trying to help governments track down citizens who used Swiss accounts to evade tax. Spain, Austria, Belgium and Argentina have also launched their own investigations.
Switzerland last year received an overall rating of "largely compliant" in an international review of how well it shares information with other countries on tax matters, but how it handles stolen data remained an issue.
Reporting by John Revill; editing by Mark Heinrich