A lawyer who was the architect of a plan to subvert the 2020 election and return Donald Trump to the White House denied all charges against him when he appeared in an Arizona court Friday.

John Eastman is the first of 18 people charged in the battleground state to appear in court over the scheme to empanel fake electors to support their favored candidate.

Others include Trump's former personal lawyer Rudy Giuliani, one-time Trump White House chief of staff Mark Meadows, attorney Jenna Ellis and campaign adviser Boris Epshteyn.

Eastman on Friday entered not guilty pleas to nine counts including conspiracy, forgery, and fraud.

If he is convicted at a trial currently set for October, the crimes could entail prison time.

Eastman told reporters outside court that the charges should never have been brought.

"I had zero communications with any of the electors in Arizona," he said. "Zero involvement with any of the litigation or the legislative hearings in Arizona. We will proceed to trial, and I'm confident, if the law is faithfully applied, I will be fully exonerated."

A US Congressional committee examining the events leading up to the January 6, 2021 attack on the Capitol recorded that Eastman was the author of memos claiming that then-vice president Mike Pence could refuse to count electoral votes from certain states, thereby preventing Congress from certifying the results.

Democrat Joe Biden won Arizona, a critical election battleground, by just over 10,000 votes, but many Republican Party officials insisted -- without evidence -- that there had been fraud and that Trump had been the real winner.

Under the US electoral college system, each state appoints electors to represent the candidate who won the most votes in the presidential poll.

Those electors sign official documents that are sent to Congress; these documents are tallied, and the winner is the person with the most electoral college votes.

Despite Trump's loss in Arizona, his representatives nonetheless signed documents saying he had won.

When Congress reconvened after the violent attacks on January 6, it ultimately ignored Arizona's fake electors and certified the genuine results, officially sending Biden to the White House.

Arizona is the fourth state to seek charges against people who tried to form an alternative slate of electors, after Michigan, Georgia, and Nevada.

Meadows, Giuliani, Ellis, and Eastman have all been charged in Georgia, alongside Trump in what is probably the most explosive of the four criminal trials he faces.

As a swing state and something of a ground zero for election conspiracy theories peddled by rightwing Republicans, Arizona is once again expected to be closely contested this November when Americans head to the polls.