A South Carolina congressman who cut his teeth as a criminal prosecutor grilled FBI Director James Comey on Thursday in an open hearing, pushing him to concede that many of Hillary Clinton's public statements about her classified email scandal – and one statement she made to Congress – were false.

Republican Rep. Trey Gowdy, who chairs a separate Capitol Hill inquest into the 2012 Benghazi terror attacks, asked Comey a series of fact-check questions that Donald Trump's presidential campaign quickly seized on, sending a video clip of the exchange to its largest email list.

Gowdy asked whether FBI investigators agreed with Clinton's claim to Congress in October 2015 that she never sent or received any items bearing classified markings.

'That is not true,' Comey declared. 'There were a small number of portion markings on, I think, three of the documents.'

Clinton's similar claims that she never emailed 'any classified material to anyone on my email' and 'there is no classified material' also didn't strike Comey as accurate.

'No, there was classified material emailed,' he said.

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PROSECUTOR: South Caroline Republican Rep. Trey Gowdy led the FBI's director through a lawyerly inquiry that resulted in declarations that Hillary Clinton lied about her classified emails

HOT SEAT: FBI Director James Comey agreed that several of Clinton's statements were false in light of the facts his agency established

'Secretary Clinton said she used one device. Was that true?' Gowdy asked.

Comey replied: 'She used multiple devices during the four years of her term as secretary of state.'

Gowdy asked if Clinton was accurate when she claimed that she and her lawyers had given the State Department all her work-related emails.

'No, we found work-related emails, thousands that were not returned,' Comey insisted.

'Secretary Clinton said neither she or anyone else deleted work-related emails from her personal account. Was that true?' Gowdy asked, continuing the line of questioning in courtroom style.

'That's a harder one to answer,' Comey answered. 'We found traces of work-related emails in – on devices or in "slack space."

'Whether they were deleted or whether, when a server changed out, something happened to them? There is no doubt that the work-related emails that were removed electronically from the email system.'

Gowdy also asked if Clinton's lawyers had read every one of her emails before deciding which ones to delete, as the former secretary of state has claimed publicly.

'No,' Comey replied.

Gowdy spent the remainder of his time asking whether investigators should have used Clinton's pattern of false statements as evidence of an effort to hide criminal conduct.

IN THE CLEAR: The Obama administration's Justice Department has closed its case without indicting Clinton for moving classified materials to an unsecured location

'In the interest of time – because I have a plane to catch tomorrow afternoon – I'm not going to go through any more of the false statements,' Gowdy snarked. 'But I am going to ask you put on your old [prosecutor's] hat.'

'False exculpatory statements, they are used for what?' he asked.

POUNCE: Donald Trump jumped on Gowdy's exchange with Comey, blasting out the video to its largest email list

Comey responded: 'Either for the substantive prosecution or for evidence of intent in a criminal prosecution.'

'Exactly,' Gowdy said. 'Intent and consciousness of guilt, right? Is that right? Consciousness of guilt and intent.'

'In your old job you would prove intent as you just referenced by showing the jury evidence of a complex scheme that was designed for the very purpose of concealing the public record, and you would be arguing in addition to concealment the destruction that you and I just talked about, or certainly the failure to preserve [documents].'

'You would also be arguing the pervasiveness of the scheme,' Gowdy offered, 'when it started, when it ended and [the] number of emails, whether they were originally classified or up-classified. You would argue all of that under the heading of "intent." You would also probably under "common scheme or plan" argue the burn-bags of daily calendar entries, or the missing daily calendar entries, as a common scheme or plan to conceal.'

'Two days ago, director, you said a reasonable person in her should have known a private email is no place to send and receive classified information. You're right. 'An average person does know not to do that,' Gowdy said.

Comey sat, stone-faced, as Gowdy vented.

'This is no average person, This is a former first lady, a former United States senator, and a former secretary of state that the president now contends is the most competent, qualified person to be president since Jefferson,' he said. 'He didn't say that in '08 but he says it now.'

'She affirmatively rejected efforts to give her a state.gov account. She kept these private emails for almost two years and only turned them over to Congress because we found out she had a private email account.'

'So you have a rogue email system set up before she took the oath of office. Thousands of what we now know to be classified emails, some of which were classified at the time,' he continued.

'One of her more frequent email comrades was in fact hacked, and you don't know whether or not she was. And this scheme took place over a long period of time and resulted in the destruction of public records – yet you say there is insufficient evidence of intent.'

Two of the three emails that Comey said Thursday held classified markings have been accounted for by the Clinton campaign. They involved calls to foreign leaders that Clinton was to make and both were sent in 2012.

The State Department said Thursday that portions were marked "c" for confidential - the lowest level of classification - in 'error.'

Even so, they were marked that information was marked as classified, contradicting Clinton's claim.

Comey left open the possibility today that Clinton didn't see the confidential stamp on the documents because they were documented improperly. Classified documents should say they are classified in the header - the emails in question did not.

'There were three e-mails, the c was in the body, in the text, but there was no header on the email or in the text,' Comey told Congressman Matt Cartwright in the hearing.

Cartwright then said, 'If Secretary Clinton really were an expert about what's classified and what's not classified and we're following the manual, the absence of a header would tell her immediately that those three documents were not classified. Am I correct in that?'

'That would be a reasonable inference,' the FBI director told him.

Clinton's campaign this afternoon pegged the exchange as a 'key development' because it 'clarified an apparent inconsistency' between Comey's remarks Tuesday and Clinton's numerous statements.

'He acknowledged, that they were improperly marked and that as a result, the materials could have been reasonably judged as not classified,' the campaign said in an email to reporters.