According to reports, the ex Julius Baer employee was found guilty of breaching bank privacy laws and coercion at a court in Zurich and fined 6,000 Swiss francs.
After the guilty verdict was announced, he was then arrested in a separate case in connection with his appearance in the UK earlier in the week.
Mr Elmer took part in a press conference at the Frontline Club in London to hand over two disks of data to WikiLeaks founder Juliun Assange.
The whisteblower alleged that the disks contained details of more than 2,000 bank accounts housed offshore for tax purposes.
He claimed that many of the details belonged to high-net individuals including bankers, celebrities and 40 politicians.
At the handover the former banker said he was providing the website with the disks as he wanted to fight against the banking industry.
âI know how the system works and I know the day-to-day business. From that point of view, I wanted to let society know what I know. It is damaging our society,â he stated at the time.
WikiLeaks is expected to leak information on a major financial institution during 2011 with many media speculation claiming that Bank of America will be the victim.
By Jim Ottewill