Facebook has presented evidence that it describes as a "smoking gun" in the ownership case filed by Paul Ceglia.
Lawyers for the social network have filed a document saying that a contract submitted by Ceglia as evidence in his ownership claim was actually a doctored version of another contract.
Having claimed that he bought an 84 per cent stake in Facebook before it became the multi-million dollar business it is today, Ceglia produced the agreement in question which was signed by both him and Facebook founder Mark Zuckerberg.
The contract appeared to show Zuckerberg agreeing to build a website called "The Face Book" or "The Page Book".
However, Facebook says that forensic testing has revealed that this contract actually relates to a website called StreetFax and makes no mention of Facebook at all.
"The court-ordered forensic testing has uncovered the authentic contract between Mark Zuckerberg and StreetFax that Ceglia attempted to conceal," the Facebook filing said.
"This smoking-gun evidence confirms what Defendants have said all along: the purported contract attached to the complaint is an outright fabrication.
"The authentic contract - which mentions only StreetFax and has nothing to do with Facebook - was found embedded in the electronic data from 2004 on Ceglia's computer."
In July of this year, Ceglia's lawyers - they of the "we did weeks of due diligence to validate his evidence" claims - became the fourth firm to ditch him and his foundering court case.
Facebook is now looking to the court for a dismissal of the case based on "the now-overwhelming evidence of Ceglia's fraud, spoliation and subterfuge."