Facebook lawyers have presented evidence they say proves a New York developer faked a contract with the social network company.
The developer's purported contract claims to entitle him to part-ownership of the $50bn social networking firm.
In April, Paul Ceglia renewed his long-running court battle to claim a 50% share of Facebook, almost a year after his first attempt stalled.
Paul Ceglia (pictured) amended his original complaint, adding a series of e-mails supposedly exchanged with Facebook founder Mark Zuckerberg.
Ceglia claimed the evidence of the e-mails supported claims he signed a contract with Zuckerberg in 2003 that entitled Ceglia to a 50% stake in Facebook, in exchange for a $1,000 investment.
In May, Facebook filed a response to Ceglia's claims, saying they were "doctored" and "fabricated", and describing the lawsuit as a brazen and outrageous fraud.
The latest filing includes an image of a two-page contract signed by Ceglia and Zuckerberg, recovered by forensics experts from Ceglia's computer.
The court hearing the case ordered Ceglia to hand over all his computers and electronic media as part of the discovery process in the case.
The image of the recovered document is difficult to read, but appears to refer only to a street-mapping database Ceglia hired Zuckerberg to work on in 2003, according to US reports.
Facebook's lawyers say the retrieved document proves the version submitted by Ceglia was doctored.
The social networking firm was barred from mentioning the forensic evidence previously by a confidentiality order that has since been modified.