BUFFALO, N.Y. — ​Last week, a state Supreme Court justice decided to allow petitioners challenging New York's new redistricting maps to gather limited discovery evidence from state legislators involved in the process.

However, when attorneys for one of the respondents appealed, the court found a procedural issue.

"The presiding justice of the Appellate Division said no, it was only a decision and it has to be an order in order to have it vacated," former Republican U.S. Rep. John Faso said.

On Wednesday, the judge officially signed an order and attorneys for the state Senate majority leader and Assembly speaker promptly appealed. The discovery is supposed to be completed by Saturday but could be stayed now as a result of the appeal.

However, Faso, who is advising the petitioners, believes expert testimony scheduled in Steuben County on Monday is even more important to the case.

"We think the evidence, the expert evidence that will be presented on behalf of the petitioners will show very clearly through use of standard statistical analysis methods that the plans for the Senate and the U.S. House are extreme gerrymanders which violate the constitution," he said.

Faso said the petitioners' primary expert is Sean Trende, an elections analyst, who the Virginia Supreme Court appointed last year as one of two special masters to help draw that state's new lines.

"He found that for each the state Senate and for the U.S. House, each having 5,000 computer generated plans, that the Democratic plan, surprise, surprise, was an extreme partisan gerrymander, moreso than any of the 5,000 statistically valid plans done by computer for the U.S. House and the State Senate," Faso said.

Faso said he believes the residents responsible for the challenge have a strong case. Under the state constitution, the judge must render a decision by April 4.