The Democratic House is looking into whether President Donald Trump lied in his written answers to Special Counsel Robert Mueller.

Trump had submitted written answers to Mueller as part of the Russian election interference probe – an investigation into whether or not the Trump Administration interfered in the 2016 presidential election.

On Monday, House General Counsel Douglas Letter said in federal court that Trump “might have provided untruthful [written] answers.” He also stated that the grand jury needed access to the 448-page Mueller Report and that the issue is a crucial part of the impeachment inquiry.

Letter’s argument followed a House bid to access the grand jury materials that Mueller collected. House Democrats have battled to see the documents for months.

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Mueller discovered considerable Russian interference, but he was unable to find substantial evidence to charge Trump.

The Democratic House’s impeachment hearing arguments Monday revolved around whether Trump lied to Mueller. The arguments followed the official seven-count conviction on Friday made of longtime Trump ally Roger Stone.

Rick Gates, former Trump deputy campaign chairman, testified that Stone and Trump spoke about incoming information that could help the Republican campaign in mid-2016. Stone was trying to obtain confidential details from WikiLeaks, at the same time. Trump told Mueller in his written statements that he did not recall discussing Wikileaks with Stone.

Gate’s testimony influenced Congress to make a request to see the 448 page report.