In a bombshell decision, a three-judge panel threw out testimony Thursday from an expert witness for GOP lawmakers in North Carolina’s partisan gerrymandering case, and it could have federal implications.

Douglas Johnson, a research fellow at the Rose Institute of State and Local Government in Claremont, Calif., testified that deceased GOP mapmaker Thomas Hofeller’s draft 2017 legislative maps were dramatically different than the maps that lawmakers ultimately enacted.

He was trying to prove that Hofeller hadn’t drawn the majority of the state’s 2017 legislative maps before the public redistricting process took place, a conclusion one of the plaintiffs’ experts presented to the court in the Common Cause v. Lewis trial.

Johnson admitted though, during cross examination, that his research was inaccurate. In the data he used to show big changes to the enacted House map from the draft Hofeller map, he omitted 11 districts in his report that showed almost 100 percent overlap between the two maps. In some instances, he would include districts with low overlap percentages in one county grouping, but not the districts in that same grouping that had a high overlap percentage.

In a similar analysis to maps produced by Common Cause North Carolina, though, Johnson included some of those high overlap districts.

When confronted with the inaccuracies during his cross examination, Johnson could not say what happened. He said he had been working late and had possibly made some coding errors.

“Sitting here today, you cannot tell the court your numbers are correct?” asked Daniel Jacobson, an attorney for the plaintiffs who cross examined Johnson.

Johnson responded, “I can tell you the idea is true.”

His inaccuracies produced overall percentages that showed Hofeller’s draft maps were more similar to the Common Cause maps than they were to the enacted maps.

That finding has been key to many of the legislative defendants’ court filings and has served as a line Republican lawmakers use when talking about the Hofeller files to the press.

Jacobson displayed during cross examination a News & Observer newspaper article quoting Pat Ryan, a spokesman for Senate President Pro Tem Phil Berger making the same claim. Johnson confirmed that he provided the information to Berger’s office and that it was based on his flawed analysis.

“I probably owe Ryan an apology,” he said on the stand.

Johnson also admitted during the cross examination that his findings that Hofeller moved a large percentage of people around in the enacted 2017 legislative map compared to his draft map was based on unweighted population calculations that should have been weighted. That error ultimately produced another unreliable statistic.

Jacobson asked the court to strike all of Johnson’s testimony from his direct examination because of his inaccurate calculations.

“Incorrect numbers can’t possibly go to weight [of this case],” he argued. “They’re just wrong.”

Patrick Lewis, an attorney for the legislative defendants, told the court that if there were some calculation errors, they don’t require a full-scale striking of Johnson’s testimony. He tried to argue for the experts’ findings regarding the Senate to stay in.

The three-judge panel returned to their chambers to consider the arguments and ultimately decided to strike all of Johnson’s testimony comparing Hofeller’s draft 2017 legislative maps to the enacted maps. They also struck testimony comparing Hofeller’s maps to the Common Cause maps.

Johnson has been the only expert the legislative defendants’ have presented thus far in the Common Cause trial who has rebutted the findings that Hofeller drew most of the 2017 enacted maps before the redistricting process.

If that finding remains at the conclusion of the trial, it could open a pathway back to the federal court. The legislative defendants convinced the federal district court in North Carolina v. Covington, a racial gerrymandering case, not to order special elections under new remedial maps in 2017.

They made repeated statements that they had not yet started drawing new districts and needed sufficient time to develop criteria, draft the plans and receive public input.

Legislative leaders didn’t approve a contract with Hofeller until the very end of June 2017, and the joint redistricting committee tasked with remedially drawing new maps didn’t even meet publicly for the first time until July 26 the same year. Hofeller’s digital files — which were turned over by his daughter after his death to the Common Cause plaintiffs — show that he had substantially completed drawing the 2017 legislative plans in June 2017, according to expert testimony.

The redistricting committee met Aug. 4 to discuss potential criteria to be used in drawing the new districts and held public comment during that meeting. Criteria for the mapmaking process was not adopted until August 10 and Hofeller wasn’t notified of it until the next day, according to a court filing from 2017 from the legislative defendants in Covington.

The Common Cause plaintiffs have already accused the legislative defendants of lying to the federal court. If proven, the federal court could sanction the legislative defendants in Covington.

The federal court in Covington ultimately obliged the legislature by not ordering a special election — despite noting in their ruling that they were prepared to. That meant the North Carolina Republican supermajority stayed in place for an extra year.

If the legislature is found to have lied to that court, it could also be important to a separate case in the state Court of Appeals, where the NAACP is challenging the Republican supermajority’s power to two constitutional amendments, one implementing a voter ID law and another implementing a tax cap.

The legislative defendants in Common Cause put on two other witnesses Thursday. Senate majority leader Harry Brown (R-Jones, Onslow) testified that he represents his Democratic and Republican constituents and tries his hardest to work across party lines within the legislature.

He was questioned during cross examination about his support for redistricting reform when he was in the minority, but said he was just making a statement.

“We all knew at this point that this bill had no chance, that it would go nowhere,” he said of a 2007 redistricting reform measure.

The other witness, Trey Hood, is a professor of political science at the University of Georgia. He continues to offer expert testimony rebutting plaintiff expert findings that the 2017 legislative plans were partisan outliers. It’s not clear if he will testify about the difference between Hofeller’s draft maps and the enacted ones.

The trial is expected to conclude tomorrow. For live updates, follow reporter Melissa Boughton on Twitter.