Former President Donald Trump’s attorneys are fighting a secret court battle to block a federal grand jury from gathering information from an expanding circle of close Trump aides about his efforts to overturn the 2020 election, people briefed on the matter told CNN.

The high-stakes legal dispute – which included the appearance of three attorneys representing Trump at the Washington, DC, federal courthouse on Thursday afternoon – is the most aggressive step taken by the former President to assert executive and attorney-client privileges in order to prevent some witnesses from sharing information in the criminal investigation events surrounding January 6, 2021.