Paul Ceglia, the man accused of trying to scam Facebook founder Mark Zuckerberg out of half his fortune, is missing, and his electronic-monitoring ankle bracelet was found at his rural New York residence.

US Marshals went to check on Ceglia in Wellsville and discovered his ankle monitor Sunday but not the 41-year-old defendant. A manhunt has begun.

Ceglia claimed that Zuckerberg promised him half of Facebook when Zuckerberg was an 18-year-old Harvard University student—and he sued Zuckerberg and Facebook. Ceglia was scheduled for federal trial in May on accusations that his lawsuit was a fraud. He has pleaded not guilty and faces a maximum 40-year prison term if convicted.

"I don't know where he is," Robert Fogg, Ceglia's attorney, said. "I haven't got a clue."

Manhattan federal prosecutors declined comment, as did Facebook. Ceglia did not return an Ars e-mail.

In an August interview with Ars, Ceglia said: "I have no interest in a plea deal of any sort. The very idea of it suggests that I have done something wrong. Of course I intend to go to trial."

Further Reading The other strange tale of Facebook’s disputed origins

According to Ceglia's lawsuit, Zuckerberg agreed to provide Ceglia with at least a 50-percent Facebook stake as part of the so-called "work for hire" contract. In return, Ceglia fronted Zuckerberg $1,000 to make it happen. The contract references a project called "The Face Book" in one place and "The Page Book" elsewhere. At least that's Ceglia's position, according to the contract he submitted to the courts (PDF).

He sued Facebook and Zuckerberg in 2010, demanding the New York federal courts enforce the contract. Along the way, he produced e-mails between himself and Zuckerberg that seemingly bolstered his position. He went through a turnstile of attorneys litigating his claims.

US Attorney Preet Bharara of the Southern District of New York charged Ceglia criminally in 2012 and said Ceglia's lawsuit was a "quick payday based on a blatant forgery" baked in "false evidence." Ceglia's lawsuit was dismissed, and the judge presiding over it said it was "predicated on a fabrication (PDF) and that plaintiff knows it."

Facebook, meanwhile, is suing the lawyers who represented Ceglia in Ceglia's initial lawsuit seeking half of Facebook.

"The lawyers representing Ceglia knew or should have known that the lawsuit was a fraud—it was brought by a convicted felon with a history of fraudulent scams, and it was based on an implausible story and obviously forged documents. In fact, Defendants’ own co-counsel discovered the fraud, informed the other lawyers, and withdrew. Despite all this, Defendants vigorously pursued the case in state and federal courts and in the media," Facebook alleged in a New York Supreme Court suit lodged in October.