If it had not been for George Papadopoulos’ lies, federal authorities may have been able to detain a man they suspected was part of Russia’s efforts to meddle in the 2016 presidential election, the special counsel said Friday night. In a court filing, special counsel Robert Mueller called for Papadopoulos to be sentenced to up to six months behind bars saying his repeated lies about contacts with Russian operatives “caused damage” to the broader investigation. Papadopoulos pleaded guilty in October of lying to the FBI and is set to be sentenced on Sept. 7.

“The defendant lied in order to conceal his contacts with Russians and Russian intermediaries during the campaign and made his false statements to investigators on January 27, 2017, early in the investigation, when key investigative decisions, including who to interview and when, were being made,” Mueller said. The lies of the former Trump adviser were not momentary lapses, but rather repeated “over the course of more than two hours, and his lies were designed to conceal facts he knew were critical.”

Robert Mueller has recommended a six-month prison sentence for George Papadopoulos, a former Trump campaign staffer, saying his "lies negatively affected the FBI's Russia investigation" https://t.co/c3Y6qUZqRp pic.twitter.com/BStXvqqFG7 — CBS News (@CBSNews) August 18, 2018

Most damaging of all was the way Papadopoulos misled agents in January 2017 about conversations he had with Joseph Mifsud, a London-based professor who reached out to him about potential “dirt” on Hillary Clinton. Mifsud was in Washington, D.C: two weeks after investigators talked to Papadopoulos but authorities allowed him to leave the country. “The defendant’s lies undermined investigators’ ability to challenge the Professor or potentially detain or arrest him while he was still in the United States,” notes the document filed Friday. “The defendant’s false statements were intended to harm the investigation, and did so.”

Mueller’s team specifically said that Papadopoulos didn’t help out investigators, which is something that could have helped him obtain a reduced sentence. “The defendant did not provide ‘substantial assistance,’ and much of the information provided by the defendant came only after the government confronted him with his own emails, text messages, internet search history, and other information,” noted the filing. Although it isn’t clear exactly why Papadopoulos lied, Mueller’s team says there is evidence that he was “attempting to secure a job with the Trump administration” and “had an incentive to protect” the White House.