The team led by special counsel Robert Mueller failed to do everything it could to determine what happened in the 2016 election, shying away from steps like subpoenaing US President Donald Trump and scrutinising his finances out of fear he would fire them, one of Mr Mueller's top lieutenants has argued in a new book.
"Had we used all available tools to uncover the truth, undeterred by the onslaught of the president's unique powers to undermine our efforts?" wrote previous prosecutor Andrew Weissmann in the first insider account of the inquiry.
"I know the hard answer to that simple question: We could have done more," he added.
The team took elaborate steps to protect its files of evidence from the risk that the Justice Department might destroy them if Mr Trump fired them and worked to keep newsmen and the public from learning what they were up to, Mr Weissmann wrote in Where Law Ends: Inside The Mueller Investigation, which Random House will publish next week.
While he speaks reverently of Mr Mueller, Mr Weissmann also says his boss' diffidence made him ill-suited for aspects of shepherding the politically charged inquiry.
He also criticised Mr Trump as "lawless" and defended himself against accusations by the President and his allies that he and other investigators were politically biased "angry Democrats"; Mr Weissmann said his personal views had no bearing on the crimes that Russian operatives and Trump aides committed.
And he elevates particular detailsfor example, emphasising that the same business account that sent hush payments to an adult film star who alleged an extramarital affair with Mr Trump had also received "payments linked to a Russian oligarch".
Mr Trump has denied the affair; his previous lawyer Michael Cohen controlled the account.
Mr Weissmann ran one of three major units for the special counsel's office. His "Team M" prosecuted Mr Trump's previous campaign chairman Paul Manafort for numerous financial crimes. The goal was to flip him and learn whatever he knew about any Trump campaign links to Russia.
Manafort had worked for pro-Russian interests in Ukraine, and the investigation uncovered ties by his business partner, Konstantin Kilimnik, to Russian intelligence.
"We would have subpoenaed the president after he refused our accommodations, even if that risked us being fired," wrote Mr Weissmann.
"It just didn't sit right. We were left feeling like we had let down the American public, who were counting on us to give it our all."
NYTIMES