RALEIGH, N.C. (CN) – An expert for Republican legislators accused of unfairly dividing North Carolina House and Senate voting districts to secure a GOP majority blamed opposing witnesses for bias in map simulations during proceedings Tuesday.
The North Carolina Democratic Party, advocacy group Common Cause and more than 30 voters are challenging district maps adopted by state lawmakers in 2017 they say were guided by partisanship and racial data.
Mathematicians and expert witnesses Jowei Chen, Wesley Pegden and Jonathan Mattingly have all testified on behalf of the challengers of the patchwork map at trial, which began July 15 in Raleigh.
Each spent almost an entire day explaining the codes, statistics and theorems they used to arrive at the same conclusion: that the oddly shaped legislative maps drawn in 2017 were extreme statistical outliers concerning how favorable they were to Republican candidates, indicating a possibility that the districts were carefully designed to do so.
But there are lies, damn lies and statistics.
An expert witness for the defendants, economist Janet Thornton, testified Tuesday that statistics used by the three scholars did not quite add up to a fair calculation of whether the enacted maps were outliers.
She told a panel of three judges the math-whiz witnesses cherrypicked with bias what elections they wanted to analyze, what scope and what standard deviations they used in order to create an outcome favorable to plaintiff’s case.
Thornton used a binomial distribution to analyze the witness’ data – using their codes – to see if she would reach a different conclusion by using different mathematical assumptions. She said that is how she discovered bias.
It was that statistical method, normally found in yes-or-no situations, that garnered criticism when Thornton testified in a similar trial in Ohio.
“Dr. Thornton also performed her own analysis using a binomial distribution, but we do not give any weight to that analysis. Dr. Thornton’s analysis used the Republican statewide vote share in congressional races ‘to predict the number of Republican seats,’ judges in Ohio said of Thorton’s testimony defending a separate map in the Buckeye State.
The analysis, the Ohio judges found, incorporates another faulty assumption that each district has a 51% chance of being won by a Republican because Republicans won 51%. Their decision has been appealed.
Thornton was adamant that this time her methods were different, though it was mentioned during cross-examination Tuesday that she assumed the same percentage chance of a Republican win for each North Carolina district she studied.
In 2017, the General Assembly adopted a set of criteria that GOP strategist Thomas Hofeller was told to use in creating new districts that would replace the racially gerrymandered districts he drew in 2011.
The U.S. Supreme Court has yet to rule on a redistricting case involving state-level political gerrymanders, and North Carolina’s districting dilemma was no exception.
After the U.S. Supreme Court declined on June 27 to get involved in the state political issue, the plaintiffs brought the case to the state court in Raleigh. They say 95 of the 170 state House and Senate districts drawn two years ago violate the North Carolina Constitution’s free speech and association protections.
The panel will determine whether Hofeller – who has since died – used partisan and racial data to draw the state voting districts, and whether those lines were illegally intended to artificially churn out Republican majorities in the General Assembly for a decade.
There are only two major federal rules on redistricting, according to the National Conference of State Legislatures. Each political district, usually drawn after the decennial census, has to be roughly equal in population. The Voting Rights Act of 1965 also outlaws district plans that intentionally or inadvertently discriminate on the basis of race, which could dilute the minority vote.
The longtime practice of gerrymandering, which is done by the political party in power to secure a stronghold in state elections, is legal unless it is done in a way that is found to violate state or federal law.
“To hold that legislators cannot take their partisan interests into account when drawing district lines would essentially countermand the framers’ decision to entrust districting to political entities,” Chief Justice John Roberts, a George W. Bush appointee, wrote for the high court last month.
Justice Elena Kagan wrote a dissenting opinion, joined by Justices Ruth Bader Ginsburg, Stephen Breyer and Sonia Sotomayor.
“The partisan gerrymanders in these cases deprived citizens of the most fundamental of their constitutional rights: the rights to participate equally in the political process, to join with others to advance political beliefs, and to choose their political representatives,” Kagan, a Barack Obama appointee, wrote.
Whether partisan gerrymandering is prohibited under the U.S. Constitution remains an unresolved question, so the groups who brought the North Carolina case seek relief under the state’s constitution.
“In future cases, one would expect map drawers not to express clearly their pure partisan intentions, and there likely would be less clear direct evidence of partisan intent. The social-science metrics and simulated maps would then become even more important considerations, for evidence of sufficiently extreme partisan gerrymanders would support the contention that a state was predominantly motivated by partisanship,” judges in the Ohio partisan gerrymandering case wrote.
The ruling on whether North Carolina will head into the 2020 elections with a different map, which the plaintiffs want drawn by an independent party, is expected in early August – and will likely be appealed to the North Carolina Supreme Court.