NEW YORK (Reuters) - A U.S. Justice Department appeals lawyer is on special counsel Robert Mueller’s team probing interference in the 2016 presidential election, Reuters has learned.

Scott Meisler, an appellate attorney with the Justice Department’s criminal division, is one of 16 lawyers who have signed on to the probe and one of only two who have not been previously identified.

Peter Carr, a spokesman for Mueller, said Meisler joined the team in mid-June.

In an investigation like Mueller’s, former U.S. Solicitor General Donald Verrilli said appeals lawyers would help determine whether the conduct being examined violates sometimes complex federal laws.

“Having people who’ve spent their careers making difficult judgments in this area would be quite valuable,” Verrilli said.

Appeals lawyers usually argue in federal circuit courts or the U.S. Supreme Court to uphold or overturn trial results. The solicitor general’s office represents the U.S. government before the Supreme Court.

Meisler is one of several appeals lawyers on Mueller’s legal team. The most senior is Deputy Solicitor General Michael Dreeben, who has argued more than 100 cases before the Supreme Court and is widely considered the Justice Department’s top criminal law expert.

Elizabeth Prelogar, an assistant solicitor general, is another appeals lawyer on the team.

Mueller, who was appointed special counsel in May, is looking into possible collusion between the Trump campaign and Russia during the election, among other matters.

Last week, his team began interviewing former and current White House officials, according to a person familiar with the matter. Russian officials have denied meddling in the U.S. election, and Trump denies any collusion by his campaign.

A 2005 Georgetown University Law Center graduate and fluent Spanish speaker, Meisler has been in his current position since 2009, aside from a recent year-long stint as an assistant solicitor general.

He has represented the government in appeals involving search warrants and seizures, motions to suppress wiretap evidence, mail fraud, wire fraud, structuring financial transactions and money laundering.