Former acting Director of National Intelligence Richard Grenell delivers a pre-recorded address to the largely virtual 2020 Republican National Convention in Washington, August 26, 2020.
CNN  — 

Former acting Director of National Intelligence Richard Grenell testified Thursday before a grand jury investigating Donald Trump’s handling of classified documents.

CNN identified Grenell as he was departing the courthouse in Washington, DC.

Grenell was subpoenaed to testify in special counsel Jack Smith’s ongoing criminal probe, according to a source familiar with the matter.

While serving in the administration, Grenell embarked upon an effort to declassify documents that were of interest to Trump because the then-president believed they could delegitimize the Russia investigation. Grenell remained in Trump’s orbit even after the former president left office and has been seen at his Mar-a-Lago resort as recently as last week.

Grenell has also commented publicly about Trump’s retention of classified documents and the former president’s still-unproven claims that the materials he kept had been declassified.

“It was all declassified papers (not accessible digitally) and kept in a former President’s office – guarded by the United States Secret Service,” Grenell said in an August 2022 tweet.

Grenell also told NBC News that month: “There is no approval process for the president of the United States to declassify intelligence. There is this phony idea that he must provide notification for declassification but that’s just silly. Who is he supposed to notify? I think it’s the height of swampism to think the president should seek bureaucrats’ approval.”

The same grand jury investigating the documents kept at Mar-a-Lago has also heard testimony from Trump’s former national security adviser Robert O’Brien. He appeared earlier this year and answered questions about conversations he had with Trump before he left office, according to the source familiar with the matter.

CNN reported at the time that O’Brien was seen at a DC federal courthouse earlier this year after receiving a subpoena from Smith’s team in both the January 6, 2021, and documents investigations.

The source told CNN that prosecutors specifically asked O’Brien about the presidential authority for declassifying documents and whether he had any conversations with Trump or those close to him about that process.

Grenell and O’Brien, given their former positions in the intelligence community, could shed light on Trump’s declassification moves around the end of his presidency. Their grand jury testimony comes in a period of intense activity from the special counsel’s office, as investigators nail down witness stories and evidence in the year-old criminal case.

Trump has consistently claimed he had the power to declassify anything he wants and could even do so just by thinking it.

He repeated a similar line during a speech after he was indicted in separate case in New York last week, when he slammed Smith and repeatedly criticized the ongoing documents probe.

CNN’s Katelyn Polantz and Kristen Holmes contributed to this report.