Supreme Court Justice Clarence Thomas raised a question Thursday that goes to the heart of Special Counsel Jack Smith's charges against former President Donald Trump.

The high court was considering Trump's argument that he is immune from prosecution for actions he took while president, but another issue is whether Smith and the Office of Special Counsel have the authority to bring charges at all.

"Did you, in this litigation, challenge the appointment of special counsel?" Thomas asked Trump attorney John Sauer on Thursday during a nearly three-hour session at the Supreme Court.

Sauer replied that Trump's attorneys had not raised that concern "directly" in the current Supreme Court case — in which justices are considering Trump's arguments that presidential immunity precludes the prosecution of charges that the former president illegally sought to overturn the 2020 election.