The man being prosecuted on allegations that he fabricated a contract that portrays Facebook founder Mark Zuckerberg promising him 50 percent of the social-networking site is gearing up to defend himself at his upcoming November criminal trial. Prosecutors say he's shaping up a doozy of a defense: that Zuckerberg hacked him.

New York federal prosecutors claim that defendant Paul Ceglia, who brought his legal troubles upon himself when he sued Zuckerberg and submitted as evidence a contract that the government claims is forged, is to argue that Zuckerberg hacked him and framed him. Those same allegations were brought up in Ceglia's civil lawsuit, which was dismissed by a federal judge who said Ceglia's contract was a "fabrication" (PDF)—a ruling that has provided fodder for the government's criminal prosecution of Ceglia.

"The Government believes that Ceglia’s theory, as he has argued in the Civil Case—with no basis for this argument—is that Zuckerberg somehow 'hacked' in to Ceglia’s computer to plant a copy of what the Government alleges is the legitimate contract. At best, Ceglia will only be able to present this baseless argument through cross examination of Zuckerberg," prosecutors wrote (PDF) in a court filing this week.

To prove his claims, Ceglia is demanding that a federal judge order Zuckerberg to hand over hard drives, mobile phones, and all e-mails used in 2003 and 2004 when Zuckerberg, as a Harvard University student, was launching Facebook. Prosecutors decried the demands as a "fishing expedition" and are urging a federal judge presiding over the case to reject the request. Facebook has repeatedly denied Ceglia's allegations.

When Zuckerberg was a Harvard student, Ceglia hired him in 2003 to perform programming work for Ceglia's online company, StreetFax, which provided photographs of intersections to insurance adjusters. The authorities claim that Ceglia "doctored or otherwise fraudulently converted" the original "Work for Hire" contract into one in which Zuckerberg agrees to provide Ceglia with at least a 50 percent Facebook stake.

A forensics report (PDF) by Stroz Freidberg said examiners found the original "Work for Hire" contract on Ceglia's computer, and it does not mention Facebook.

The authorities allege that Ceglia replaced the first page of the 2003 contract with a page of his own creation, to reflect a stake in Facebook. The columns, margins, and spacing on the first page differ significantly from the layout on the second page, the authorities allege. Also, the first page of the document refers to StreetFax LLC, the company Ceglia hired Zuckerberg to work on, but Ceglia claimed StreetFax as a limited liability corporation four months after the second page was signed by Zuckerberg.

Ceglia's attorneys did not immediately respond for comment.

Facebook has a market cap of about $170 billion.