The drama of the Facebook story heightened last week as a man with a shady past used old e-mails and a powerful law firm to press his claim to half the online social networking firm.

A legal claim filed last year by Paul Ceglia and deemed dubious by many was being re-evaluated after lawyers at DLA Piper amended the complaint to include e-mails that appear to back the New York State man’s position.

Mr Ceglia contended that he hired then Harvard University student Mark Zuckerberg in 2003 to do software coding for a StreetFax website and wound up providing seed money for what Zuckerberg than called “the face book.”

Evidence presented by Mr Ceglia, whose background includes criminal charges for fraud and a conviction for possession of hallucinogenic mushrooms, included a signed contract and e-mail exchanges.

“This is a fraudulent lawsuit brought by a convicted felon, and we look forward to defending it in court,” Facebook lawyer Orin Syder of Gibson, Dunn & Crutcher said in a statement.

“From the outset, we’ve said that this scam artist’s claims are ridiculous and this newest complaint is no better.”

Mr Ceglia claims he provided Zuckerberg with $2,000 in exchange for half of what is now Facebook, which boasts more than 600 million members and was recently valued at $50 billion.