Expert Reports

Moon has served as an expert witness in a variety of court cases related to race, redistricting, and the VRA. What role does mathematics and data science play in the court?

Reports

• Texas congressional (LULAC v. Abbott)

  Moon Duchin

  07 September 2025

  This case consolidated a number of different ones that had been active since 2021. The initial post-Census districting plan was challenged, but before that decision was reached, the State replaced the plan with a new and more aggressively partisan alternative. A preliminary injunction hearing in October 2025 resulted in a federal court blocking the new plan as a racial gerrymander that was likely to be unconstitutional, not just a now-permissible partisan gerrymander. SCOTUS stepped in and stayed the injunction. This report (Duchin’s 5th in this case) delineates race-vs.-party distinctions. Read the report here.

  Status: Federal court, ongoing.

• Pennsylvania congressional (Carter v. Chapman)

  Moon Duchin

  24 January 2022

  In this split-control state, the Republican legislature put forward a congressional plan (lightly adapted from a citizen-drawn plan!) and the Democratic governor vetoed it. This led to a hearing in which many plaintiffs’ groups presented maps for consideration. The basis for decision was the “Free and Equal Elections” clause in the state constitution, which meant that most experts focused on the partisan fairness of the plans. The state supreme court ultimately adopted a plan proposed by one of the plaintiff groups. This report focuses on how to understand partisan properties of a plan.

  Status: State court, decided 2022.

• North Carolina congressional and legislative (Moore v. Harper)

  Moon Duchin

  23 December 2021

  Another case based on the state constitution and largely but not entirely focused on partisan fairness. This report focuses on a standard that Duchin dubbed “Close Votes, Close Seats,” later cited by the state Supreme Court decision in throwing out the State’s Congressional plan and appointing a special master to draw a new one. This case was appealed up to SCOTUS and became elevated to a question about whether courts can second-guess legislatures at all (the so-called “Independent State Legislature Theory”). SCOTUS upheld the NC decision – but then just a few months later, several seats flipped on the state supreme court, and the new court simply reversed this decision and reinstated the original map. Read the report here.

  Status: State court, decided 2022, reversed 2023.

• Alabama congressional (Allen v. Milligan)

  Moon Duchin

  10 December 2021

  This was a high-profile Voting Rights Act case arguing that Black voters in Alabama had their votes impermissibly diluted by the State’s districting plan. Black voters make up about 2/7 of Alabamians and vote quite cohesively, but the challenged plan was drawn to ensure that only 1 out of 7 districts would offer an opportunity to elect a candidate of choice. This report mainly offers an existence proof: it is possible to draw a reasonably configured plan with two majority-Black districts. (In VRA law, majority-minority districts are not necessary at the end of the day, but you have to show that they are possible.) In fact, four different possibilities are presented – Plans A,B,C, and D – and they balance traditional districting principles in a variety of ways. Read the report here.

  Status: Federal court, decided 2022, affirmed 2023.

For more expert reports, please contact the Lab directly.