More than half of the bogus Georgia electors who were convened in December 2020 to try to keep former President Donald J. Trump in power have taken immunity deals in the investigation into election interference there, according to a court filing on Friday and people with knowledge of the inquiry.

In addition, Craig A. Gillen, the former deputy independent counsel in the 1980s-era Iran Contra scandal, has been hired to represent a fake elector who could still face criminal charges, David Shafer, the head of the Georgia Republican Party. Mr. Gillen specializes in cases involving racketeering, which is among the charges being weighed by Fani T. Willis, the district attorney of Fulton County, Ga.

Ms. Willis’s office has spent more than two years investigating whether the former president and his allies illegally meddled in the 2020 election in Georgia, which Mr. Trump narrowly lost to President Biden. A special grand jury that heard evidence in the case for roughly seven months recommended more than a dozen people for indictments, and its forewoman strongly hinted in an interview with The New York Times in February that Mr. Trump was among them.

Ultimately, it will be up to Ms. Willis to decide which charges to seek before a regular grand jury, which she has said she will do after a new jury is seated in mid-July. Her case is focused in part on a plan to create the slate of electors pledged to Mr. Trump in the weeks after the 2020 election despite Mr. Biden’s victory in Georgia.