A judge on Wednesday ordered the former White House chief of staff Mark Meadows to testify before a special grand jury investigating whether Donald Trump and his allies illegally tried to overturn Georgia’s results in the 2020 election.

Meadows is a key figure in the investigation. He traveled to Georgia, sat in on calls with state officials and coordinated and communicated with influencers either encouraging or discouraging the pressure campaign.

The Fulton county district attorney, Fani Willis, opened the investigation last year. Meadows is just one of several Trump associates and advisers whose testimony Willis has sought.

Because Meadows does not live in Georgia, Willis, a Democrat, had to get a judge where he lives, in South Carolina, to order him to appear. Edward Miller, a circuit court judge in Pickens county, ordered Meadows to testify, a Willis spokesperson confirmed.

Meadows’s attorney, Jim Bannister, said his client was “weighing all options” including appeals.

“Nothing final until we see the order,” he said.

Willis has been fighting similar battles in courts around the US. An appeals court in Texas has indicated it may not recognize the validity of the Georgia summonses. Lindsey Graham, a Republican senator from South Carolina, asked the US supreme court to intervene after a federal appeals court ordered him to testify.

In the petition seeking Meadows’s testimony, Willis wrote that he attended a 21 December 2020 meeting with Trump and others “to discuss allegations of voter fraud and certification of electoral college votes from Georgia and other states”.

The next day, Willis wrote, Meadows made a “surprise visit” to Cobb county, just outside Atlanta, where an audit of signatures on absentee ballot envelopes was being conducted. He asked to observe but was not allowed to because the audit was not open to the public, the petition says.

Meadows also sent emails to justice department officials alleging voter fraud in Georgia and elsewhere and requesting investigations, Willis wrote. And he took part in a 2 January 2021 call with the Georgia secretary of state, Brad Raffensperger, during which Trump suggested Raffensperger “find” enough votes to overturn the president’s loss in the state.

According to a transcript of the call, Meadows said Trump’s team believed that “not every vote or fair vote and legal vote was counted. And that’s at odds with the representation from the secretary of state’s office.” He also said he hoped they could agree on a way “to look at this a little bit more fully”. Raffensperger disputed the assertions.

After the election, Meadows was widely seen in the White House as a chief instigator of Trump’s fixation on the election, passing along conspiracies about fraud other officials were forced to swat down. He pushed one theory that people in Italy had changed votes in the US with satellite technology, a claim the former justice department official Richard Donoghue labeled “pure insanity”.

In a court filing this week, Meadows’s lawyer argued that executive privilege and other rights shield his client from testifying.

Bannister asserted that Meadows has been instructed by Trump “to preserve certain privileges and immunities attaching to his former office as White House chief of staff”. Willis’s petition calls for him “to divulge the contents of executive privileged communications with the president”, Bannister wrote.

Meadows also invoked that privilege in a fight against subpoenas issued by the House January 6 committee. Meadows has been fighting investigations of the Capitol attack and has avoided having to testify. He turned over thousands of texts to the House committee before refusing an interview.

The House held Meadows in contempt of Congress but the justice department declined to prosecute.

Special grand juries in Georgia cannot issue indictments. Instead, they can gather evidence and compel testimony and recommend further action, including criminal charges. It is up to the district attorney to decide whether to seek an indictment from a regular grand jury.