An assistant United States attorney, Rebekah Donaleski, said during the hearing that the government was already using a “filter team” to review which materials should be privileged and shielded from prosecutors. She said prosecutors would discuss with the defense team whether there was any basis to invoke executive privilege.
“We are attuned to those concerns,” Ms. Donaleski said.
The prosecutors in the case, from the office of the United States Attorney for the Southern District of New York, along with the F.B.I. have conducted searches of email and social media accounts, electronic devices and several unidentified premises, she said. They have also subpoenaed records for more than 50 bank accounts.
Mr. Parnas and Mr. Fruman, immigrants from the former Soviet Union who became American citizens, were arrested on Oct. 9 at an airport in Washington, D.C., with one-way tickets to Frankfurt. They each face four criminal charges related to violations of campaign-finance law.
Prosecutors also have linked Mr. Parnas and Mr. Fruman to an attempt to recall the United States ambassador to Ukraine, Marie L. Yovanovitch, who had become a focus of criticism from many of Mr. Trump’s allies.
House Democrats last month opened an impeachment inquiry investigating whether her removal was connected to Mr. Trump’s attempt to gather damaging information in Ukraine about Mr. Biden, who is a leading candidate for the Democratic presidential nomination.