Harvard Law School professor Alan Dershowitz speculated Tuesday that George Papadopoulos, former foreign policy adviser to President Trump's campaign, may have worn a wire to get on-the-record comments about the campaign's ties to Russia.

Papadopoulos was arrested in July, but did not plead guilty to charges of making false statements to the FBI until October.

He may have worked special counsel Robert Mueller during that time, and Dershowitz speculated that he may have worn a wire to get evidence from Trump associates as part of a deal.

"That's why they would put a wire on him: they want self-proving evidence. They don't want to have to rely on him and his testimony because any good defense attorney would start out by saying 'tell us all the lies you engaged in — now why should we believe you now because you are getting a deal, you would sell your mother for this deal,'" Dershowitz told Fox News.

"He is not a credible witness. You don't put on a witness because he admitted lying already twice at least," Dershowitz said.

Even if Papadopoulos were unable to meet directly with Trump or Manafort as part of a potential FBI effort to get their comments on the record, Dershowitz said they may be using the 30-year-old witness to get to others and then use those people.

"What Mueller's plan is, domino by domino. He has three dominos now and try to squeeze them to get another domino to see if they can get somebody closer to the president," Dershowitz said. "They may have a wire, not against the president, but they have a wire against some other person. They go to that other person and say not to the public, 'we have you on the wire, now we would like you to wear a wire.'

"And then we would like another guy to wear a wire. We would like you to provide evidence. You don't reveal publicly your investigation until you have it all completely down pat. Obviously what we learned is they don't have the evidence at this point. They are still in the process of gathering it," he added.