WATCH: Jack Smith explains why Trump was the only defendant charged in Jan. 6 case

Rep. Brad Knott, R-N.C., questioned former special counsel Jack Smith on Thursday in a hearing focused on Smith's investigations into President Donald Trump's mishandling of classified documents and role in the Jan. 6 attack.

Watch Knott and Smith's remarks in the video player above.

Knott said only one defendant — Trump — was the target of the indictment in the Jan. 6 case, despite six co-conspirators being identified in the document.

Smith said that his team believed that there was proof to charge other people, saying he "was in the process of making that determination when our work was concluded."

The career prosecutor then said that it's correct that Trump was the only named defendant in that case because he, "in my estimation, was the person most culpable for the crimes charged."

READ MORE: Jan. 6 attack 'does not happen' without Trump, Jack Smith told Congress

When Knott reiterated that Smith only charged one person, Smith said that decision was "consistent with the federal principles of prosecution, which emphasize the degree of someone's culpability in making a charging decision," and Trump was that person.

The hearing is an opportunity for the career prosecutor to publicly offer his inside perspective on the investigations, which both led to unprecedented indictments. Both were scuttled once it was clear that Trump would return to the Oval Office; Department of Justice policy prevents prosecution of a sitting president.

Republicans and the president have accused Smith of pursuing a politically motivated case against the president. Trump has denied wrongdoing while attacking Smith, calling him a "criminal" who ought to be investigated and "put in prison."

Smith defended his investigations in an hourslong closed-door meeting with lawmakers in December, saying he said he had "proof beyond a reasonable doubt" of what his investigations laid out. He's denied accusations of bias.