Manhattan Assistant District Attorney Peirce Moser, who is heading the team prosecuting four former Dewey & LeBoeuf lawyers for financial fraud, has been appointed as chief of the office’s Tax Crimes Unit.

“Under Peirce’s leadership, we will continue, and expand, our commitment to safeguarding the coffers of our city and state,” District Attorney Cyrus Vance Jr. said in a statement Tuesday.

The unit oversees long-term investigations and prosecutions to ensure the city and state are paid taxes they are owed. It recovered approximately $11 million in unpaid taxes last year, according to the D.A.’s office.

Moser’s expertise in tax law spans his entire career. In 1999 he graduated from the University of Virginia School of Law, where he was a senior editorial board member of the Virginia Tax Review. He clerked for U.S. Court of Appeals for the Fifth Circuit Chief Judge Carolyn Dineen King. He also practiced tax law for Wilmer Cutler Pickering Hale and Dorr, then Bingham McCutchen, before joining the Manhattan District Attorney’s office in 2006.

He joins the Tax Crimes Unit from the Major Economic Crimes Bureau.

In addition to the Dewey case, Moser has handled major financial crimes including the prosecution of the late Brooke Astor’s son Anthony Marshall for fraud associated with her estate; the prosecution of Robert Joel “Joe” Halderman for attempting to extort $2 million from David Letterman; and the prosecution of tax accountant Joseph Cilibrasi for embezzling money from his entertainment industry clients.

Moser will continue prosecuting the Dewey defendants, who have been charged with larceny and securities fraud in a four-year scheme to “cook the books,” in the words of one defendant.