Former Vice President Mike Pence has testified before the federal grand jury investigating the 2021 U.S. Capitol riot and efforts by then-President Donald Trump to overturn his defeat to Joe Biden in the 2020 presidential election, the New York Times reported Thursday.

The testimony — which could provide critical insights into confidential deliberations within the Oval Office in the days before and after the Capitol riot — came less than 24 hours after the U.S. Court of Appeals for the District of Columbia rejected Trump’s 11th-hour attempt to block Pence’s testimony.

Pence appeared at the E. Barrett Prettyman federal courthouse at around 9 am in a motorcade of SUVs and spent several hours before the grand jury. The motorcade left the courthouse’s underground garage at about 4.30 pm, per NBC News.

The closed-door deposition was a milestone in the Department of Justice (DOJ)’s criminal investigation into the aftermath of the 2020 investigation. It was also the first time in modern history a vice president was compelled to testify against a president he once loyally served.

A target of an intense Trumpworld pressure campaign in the lead-up to January 6, 2021, Pence is expected to divulge under oath private, direct conversations with Trump and his inner circle members, who unsuccessfully pressed him in the days leading up to the Capitol riot to block the certification of the 2020 election result.

Pence rejected Trump’s entreaties — including on a private phone call on the morning of Jan 6 — to block the certification of Joe Biden’s victory in his capacity as the President of the Senate, a ceremonial role to oversee Congress’s Electoral College vote count.

The former vice president, who is reportedly mulling a 2024 bid for the White House, has spoken extensively about his refusal to aid Trump’s efforts to retain power despite losing the election.

“The president's words were reckless, and they endangered my family and everyone at the Capitol building," Pence told the Associated Press last year.

“I had no right to overturn the election,” Pence said at the annual Gridiron Dinner in DC last month. “And I know that history will hold Donald Trump accountable.”

Court Battle Over Testimony

Although Pence had been open about the widening rift between him and his former boss in the final weeks of the Trump presidency, he refused to recount it under oath.

However, a subpoena for his testimony was issued in early February by Jack Smith, the special counsel appointed by the DOJ to oversee, amongst others, its criminal investigation into Trump’s efforts to upend the 2020 election.

The subpoena came after talks last year between Pence’s advisers and DOJ officials about Pence providing testimony in the criminal investigation into Trump’s 2020 post-election efforts broke down, the Times noted in its report.

Pence and Trump challenged the subpoena. Pence argued he qualified for congressional immunity under the Constitution’s “speech or debate clause” and, thus, couldn’t be compelled to testify about his role in overseeing the congressional certification of Biden’s victory.

Trump, on the other hand, cited executive privilege — a legal doctrine shielding communications between a president and some of his advisers to preserve the secrecy in presidential decision-making — as grounds for challenging the subpoena.

After hearing arguments from all parties to the case — Trump, Pence, and special counsel Smith — Chief U.S. District Judge James E. Boasberg rejected Trump’s assertions but allowed Pence to discuss only matters about potentially criminal acts Trump committed.

Pence’s legal counsel didn’t appeal Boasberg's ruling, but Trump’s team unsuccessfully sued at the appeals court to delay or vacate it, citing executive privilege.

In a March 28 interview with Newsmax, Pence said he was happy the court accepted his speech and debate clause argument and reiterated that he had nothing to hide.

“I believe we did our duty that day under the Constitution of the United States, and in this matter, I thought it was important that we stand on that constitutional principle again,” Pence said.

In an interview with CBS’s Face the Nation, which aired on Sunday, Pence assured CBS’s Robert Costa that “people can be confident that we'll — we'll obey the law. We'll comply with the law.”