A former federal prosecutor has joined the Manhattan D.A.’s team investigating the Trump family business.
As the Manhattan district attorney’s office steps up the criminal investigation of Donald J. Trump, it has reached outside its ranks to enlist a prominent former federal prosecutor to help scrutinize financial dealings at the former president’s company, according to several people with knowledge of the matter.
The former prosecutor, Mark F. Pomerantz, has deep experience investigating and defending white-collar and organized crime cases, bolstering the team under District Attorney Cyrus R. Vance Jr. that is examining Mr. Trump and his family business, the Trump Organization.
The investigation by Mr. Vance, a Democrat, is focused on possible tax and bank-related fraud, including whether the Trump Organization misled its lenders or local tax authorities about the value of his properties to obtain loans and tax benefits, the people with knowledge of the matter said, requesting anonymity because of the sensitive nature of the investigation.
Mr. Trump has maintained he did nothing improper and has long railed against the inquiry, calling it a politically motivated “witch hunt.”
In recent months, Mr. Vance’s office has broadened the long-running investigation to include an array of financial transactions and Trump properties, as prosecutors await a ruling from the United States Supreme Court that could give them access to Mr. Trump’s tax returns.
Prosecutors have said the tax returns and other financial records are vital to their inquiry — and the Supreme Court has delayed a final decision for months.
Manhattan prosecutors have also subpoenaed the Trump Organization for records related to tax deductions on millions of dollars in consulting fees, some of which appear to have gone to the former president’s daughter Ivanka Trump.
The Trump Organization turned over some of those records last month, though the prosecutors have questioned whether the company has fully responded to the subpoena, the people with knowledge of the matter said.
The Trump Organization declined to comment, but in the past, lawyers for the company have said that its practices complied with the law and have called the investigation a “fishing expedition.”
Mr. Pomerantz, 69, was sworn in earlier this month to serve as a special assistant district attorney, according to Danny Frost, a spokesman for the district attorney, who otherwise declined to comment on the inquiry. Mr. Pomerantz will work solely on the Trump investigation.
Mr. Pomerantz was a federal prosecutor in the United States attorney’s office in Manhattan, where he rose to lead the appellate unit before leaving in 1982. In private practice, he developed a specialty in organized crime and was involved in a 1988 case that helped determine the legal definition of racketeering.
Mr. Pomerantz returned to the Manhattan U.S. attorney’s office to head the criminal division between 1997 and 1999, overseeing major securities fraud and organized crime cases, perhaps most prominently against John A. Gotti, the Gambino boss.
The hiring of an outsider is a highly unusual move for a prosecutor’s office, but the two-and-a-half-year investigation of the former president and his family business is unusually complex.