A US prosecutor has told jurors at Steve Bannon’s criminal trial that the prominent former presidential adviser to Donald Trump decided he was “above the law” in defying a subpoena from the congressional committee investigating last year’s attack on the US Capitol.

The prosecution and defence delivered opening statements after jurors were selected in the trial, with the government’s first witness then testifying.

Evan Corcoran, a lawyer for Mr Bannon, said Mr Bannon did not ignore the subpoena and in fact engaged with the committee in the belief it would negotiate with his lawyer and that its deadlines “were not fixed – they were flexible”.

Mr Bannon, 68, has pleaded not guilty to two misdemeanour counts of contempt of Congress brought after he declined last year to provide testimony or documents to the Democratic-led House of Representatives select committee.

The subpoena issued last September, prosecutor Amanda Vaughn told jurors on Tuesday, “wasn’t optional. It wasn’t a request. And it wasn’t an invitation. It was mandatory.”

“The defendant decided he was above the law,” Ms Vaughn said. “That’s why we’re here today.”

Ms Vaughn said the committee had reason to believe Mr Bannon might have information about the events leading up to the January 6, 2021, riot.

Mr Trump’s supporters stormed the Capitol and attacked police in a failed effort to block formal congressional certification of his 2020 election loss to Democrat Joe Biden.

Mr Bannon “didn’t get stuck on a broken down Metro car”, Ms Vaughn said of the defendant’s refusal to comply with the subpoena, referring to the Washington area’s subway system.

Instead, the case was about “the defendant thumbing his nose” at the normal process of government, Ms Vaughn said.

Mr Corcoran said committee staff and lawyers for proposed witnesses almost always negotiated – and witnesses often appeared at a date later than the one specified in a subpoena.

“That’s the process,” Mr Corcoran said.

Kristin Amerling, the committee’s general counsel, was the first prosecution witness.

“When the committee issues subpoenas with deadlines, is it important to the committee for people to comply with the deadlines?” Ms Vaughn asked Ms Amerling.

“Absolutely,” Ms Amerling replied. “The select committee is looking at a violent assault on the United States Capitol, on law enforcement, on our democratic institutions. We have a limited amount of time.”

In explaining the panel’s interest in hearing from Mr Bannon, Ms Amerling noted that he had told a podcast the day before the riot that “all hell is going to break loose tomorrow” and that the committee wanted to learn whether he had advance knowledge of the attack.

Twelve jurors and two alternates – nine men and five women – were selected, with US District Judge Carl Nichols presiding over the trial.

Judge Nichols previously ruled that Mr Bannon could not claim he failed to comply with the subpoena because he believed his documents and testimony were protected by a legal doctrine called executive privilege that can keep certain presidential communications confidential.

The judge also has barred Mr Bannon from telling jurors that he relied upon advice from his lawyer, who told him there were valid legal reasons he could fail to respond to the subpoena.

Mr Bannon reversed course this month and said he wanted to testify before a public committee hearing, nearly 10 months after defying the subpoena.

There has been no indication of any plan to have him do so, as the committee likely would want him to first testify in closed sessions in order to cover a wide range of matters. Mr Trump told Mr Bannon he was waiving any executive privilege claim.

As a top adviser to the Republican Trump’s 2016 presidential campaign who later served as White House chief strategist, Mr Bannon helped articulate the “America First” right-wing populism and fierce opposition to immigration that helped define Trump’s presidency.