A US federal appeals court upheld on Friday the conviction of Steve Bannon (pictured), a former top adviser to former president Donald Trump, for defying a subpoena from the congressional panel that investigated the January 6, 2021 attack on the US Capitol.The ruling brings Bannon a step closer to serving a four-month prison sentence for contempt of Congress, but he can still mount additional appeals.Bannon was convicted in 2022 of two misdemeanour counts of contempt of Congress for refusing to turn over documents or testify to the House of Representatives committee that investigated the Capitol riot.He has been allowed to remain free during his appeal.Bannon, a key figure on the American right, argued on appeal that his lawyer advised him he did not have to comply with the subpoena and therefore he did not intend to commit a crime.Bannon’s argument would “hamstring Congress’s investigatory authority”, by making it more difficult to prosecute witnesses who spurn congressional investigations, a three-judge panel of the US Court of Appeals for the District of Columbia Circuit found.A lawyer and spokesperson for Bannon did not immediately respond to requests for comment.He can appeal the ruling to the full DC Circuit court and the US Supreme Court.The Democrat-led House panel investigated Trump’s efforts to subvert the 2020 election results, which culminated on January 6, 2021 when a mob of his supporters breached the Capitol in an attempt to stop the formal certification of the vote.The committee sought information from Bannon, who predicted on a podcast the day before the riot that “all hell is going to break loose tomorrow”.Bannon refused to co-operate with the committee’s probe, which he attacked as politically motivated.Former Trump trade adviser Peter Navarro is currently serving a four-month prison sentence for defying a subpoena from the same committee.Navarro, 74, is the highest-ranking former member of the Trump administration to spend time behind bars for actions stemming from the former Republican president’s efforts to overturn the results of the 2020 election.Bannon served in the White House as chief strategist for the first seven months of Trump’s term, leaving reportedly because of conflicts with other top staffers.In 2020, Bannon was charged with wire fraud and money laundering for taking for personal use millions of dollars contributed by donors toward the construction of a border wall with Mexico.While others were found guilty in the scheme, Trump issued a blanket pardon to Bannon before leaving office in January 2021, leading to the dismissal of the charges against him.