Mark Zuckerberg’s backyard privacy showdown has grown more tangled with competing claims about a mysterious African prince and a private eye accused of bullying a witness.

The Facebook Inc. founder is accused in a real estate developer’s lawsuit of reneging on a promise to introduce him to Silicon Valley’s elite as part of a $1.7 million deal that ended plans for a mansion with a view into the 31-year-old billionaire’s bedroom.

Zuckerberg’s lawyers claim that after digging into developer Mircea Voskerician’s version of events, they aren’t convinced a prince who purportedly offered 2 1/2 times that for the property rights really exists.

Voskerician contends the true objective of Zuckerberg’s detective was to intimidate a witness.

The current squabble comes in a dispute that has already exposed internal Facebook e-mails and spurred a $39 million real estate shopping spree to protect the tranquility of Zuckerberg’s two-story home in Palo Alto, California. As the two sides cast aspersions aimed at undermining the other’s credibility, the case moves closer to a trial scheduled for November that may air even more unseemly details.

Whether the developer conjured up a competing offer to make his lawsuit more compelling may prove to be one of those details.

‘Discount’ Price

Zuckerberg’s lawyers, aided by San Francisco private investigator Zachary Fechheimer, have been investigating a $4.3 million offer Voskerician said he turned down. The developer said he gave Zuckerberg a “discount” price because of the business introductions included in the deal.

James Sagorac, a friend of Voskerician’s who was acting as an intermediary for the original offer, initially refused to name the client he was representing, Zuckerberg’s lawyers said. Under a judge’s order, Voskerician’s lawyer provided Zuckerberg with contact information for Sagorac’s client, identified as a lawyer in South Africa, according to a state court filing in San Jose, California.

The South African, who Zuckerberg’s lawyers said they weren’t able to confirm was registered as a lawyer in that country, disclosed that the offer was made on behalf of a prince, according to the filing.

While refusing to identify the prince, the South African “displayed remarkable interest” in the lawsuit against Zuckerberg, “probing with particular focus on exactly when Mr. Zuckerberg intended to settle the case,” according to Zuckerberg’s filing. “When told no payoff was in the works, the purported lawyer expressed disappointment and disapproval.”

Voskerician’s Credibility

The Facebook chief executive is trying to undermine Voskerician’s credibility so that a judge or jury will find it hard to believe what he alleges, said David Min, a law professor at the University of California at Irvine who’s been following the court battle.

If Voskerician was “in some sort of conspiracy to inflate the apparent price, he seems far less believable in his testimony as far as other claims, such as the promise from Zuckerberg,” Min said.

While Zuckerberg’s lawyer claims the private eye is just doing his job to examine Sagorac’s “bona fides,” Voskerician attorney David Draper sees it differently.

Smear Allegation

The investigation is part of an “all-out effort to publicly smear” Sagorac, who is “irrelevant” to the lawsuit, and a diversion from the central fraud claims against Zuckerberg, Draper said in a court filing.

When Fechheimer visited the Milwaukee area to talk to Sagorac’s relatives, he told them Sagorac was “the mastermind behind a scheme to swindle money out of Mark Zuckerberg,” according to the filing. The investigator inquired whether Sagorac’s mother had been institutionalized. Sagorac filed a police report in Menlo Park, California, after his girlfriend was contacted by Fechheimer.

“I feel that my family and my girlfriend have been contacted in an effort to slander me and to intimidate me from testifying in this case,” Sagorac said in a court filing.

Patrick Gunn, a lawyer representing Zuckerberg, and Fechheimer declined to comment on the court filings. Draper also declined to comment.

Draper has asked a judge to let him interview Fechheimer. Zuckerberg’s lawyers object, saying that would violate attorney- client confidentiality. A hearing on that dispute is set for Tuesday.

The case is Voskerician v. Zuckerberg, 114CV264667, Superior Court of the California, County of Santa Clara (San Jose).