A United States appeals court has upheld a ruling granting a Democratic-led House of Representatives committee access to material that had been redacted from former special counsel Robert Mueller's report on Russian interference in the 2016 election.

In a two-to-one decision, a three-judge panel of the US Court of Appeals for the District of Columbia Circuit said the law requires the Justice Department to produce grand jury material from Mueller's investigation to the House Judiciary Committee, which has been investigating the president's actions during the probe.

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Representative Jerrold Nadler, who chairs the committee, subpoenaed the material in the spring of last year and in July submitted a petition to a federal judge as part of a continued investigation into whether the president and his inner circle abused his power or lied during the Mueller probe. If wrongdoing is found, the House could bring new articles of impeachment against the president.

The petition requested "all portions" of Mueller's report, any "underlying transcripts or exhibits" referenced by redacted portions of the report, and transcripts of grand jury testimony or exhibits related to, among others, Trump's knowledge of Russian attempts to interfere in the 2016 election or any crimes committed by his associates.

In her opinion, Judge Judith Rogers wrote that because Mueller "stopped short" of reaching conclusions about Trump's conduct to avoid stepping on the House's impeachment power, "the Committee has established that it cannot 'fairly and diligently' make a final determination about the conduct described in both volumes of the Mueller Report 'without the grand jury material referenced' therein."

Russian influence campaign

Mueller submitted his report to US Attorney General William Barr in March 2019 after completing a 22-month investigation that detailed Russia's campaign of hacking and propaganda to boost Trump's candidacy in the 2016 election as well as extensive contacts between Trump's campaign and Moscow.

In regards to Trump, Mueller said the inquiry did not find "sufficient evidence" that he or his team colluded with Russia. The report also did not conclude that Trump was guilty of obstructing the investigation, but did not exonerate him either.

Barr, a Trump appointee whom Democrats have accused of trying to protect the president politically, released the 448-page report in April 2019 with some parts redacted.

The president has long called the probe a partisan "witch-hunt". However, while a subsequent investigation by Department of Justice Inspector General Michael Horowitz released in December found numerous errors in how the investigation was conducted, it did not find evidence of political bias.

Several Trump associates, notably Republican operative Roger Stone and former National Security Advisor Michael Flynn, have been charged with crimes related to the probe. Meanwhile, the president has called for all cases related to Mueller's investigation to be "thrown out".

The Department of Justice could ask the same appeals court to reconsider Tuesday's decision or appeal the ruling to the US Supreme Court.