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The Trump administration has refused to turn over 20 previously undisclosed emails about the freeze on security aid to Ukraine that is now at the center of the impeachment of President Donald Trump. Now a federal judge may decide whether the public will get to see them.

The New York Times filed a public records request and then a lawsuit for emails between a top aide to acting Chief of Staff Mick Mulvaney, Robert Blair, and Michael Duffey, the Office of Management and Budget official in charge of releasing security assistance for Ukraine. On Friday, the White House refused. It acknowledged the emails but declined to turn them over, even in a redacted format, arguing that they are protected by public record law exemptions for disclosures that would “inhibit the frank and candid exchange of views that is necessary for effective government decision-making.” In response, the Times plans to ask the judge, DC federal Judge Amy Berman Jackson, to swiftly compel the documents’ release.

The documents—whether released or not—are likely to play a role in the Senate’s impeachment deliberations. Central to the question of whether Trump should remain in office is whether he abused his power for personal gain—in particular, withheld crucial security aide in hopes of extracting politically-damaging investigations against a political opponent. Senate Minority Leader Chuck Schumer is pushing for documents and witness testimony to be considered during the trial and has named both Blair and Duffey as key witnesses that should testify.

The White House is now openly defying a federal court order to release emails between key players in the Trump-Ukraine scandal. President Trump: If you’re listening, release the emails! What are you so afraid the American people will see? https://t.co/sbDJGhuUgD — Chuck Schumer (@SenSchumer) January 4, 2020

This request has deadlocked negotiations over how the Senate trial will unfold. Senate Majority Leader Mitch McConnell has not committed to calling witnesses and announced instead that he will coordinate with the White House on how to proceed. It remains unclear when the Senate will begin its trial.