David Horniak litigates complex, high-stakes civil and criminal cases around the country at both the trial and appellate levels.  He represents clients in a broad range of substantive areas of litigation, with a particular focus on tax, patent, and food and beverage disputes.  Among other things, David has guided clients through investigations and litigation brought by federal and state tax authorities; pharmaceutical patent infringement actions brought under the Hatch-Waxman Act; and class actions brought under state consumer-protection laws.  His experience includes representing individuals and major corporations, and he has argued numerous motions, had an active role in multiple trials, and authored successful dispositive motions and appeals.  He was named to the Washington, D.C. “Rising Stars” list in the 2014–2019 editions of Super Lawyers.

Born in California and raised in Minnesota, David graduated with honors from Dartmouth College, where he rowed varsity crew and was selected Academic All Ivy in the 2002 and 2003 seasons.  After college, he managed operations for a distribution company in the Chicago area, where he assisted in the design and expansion of that company’s facility.  David received his J.D. from the University of Michigan Law School, where he graduated magna cum laude, was a member of the Order of the Coif, and served as an editor of the Michigan Law Review.  Following law school, David clerked in Seattle for Judge Ronald M. Gould of the U.S. Court of Appeals for the Ninth Circuit before joining Williams & Connolly in 2010.  He lives in the District of Columbia with his wife and three sons.

Representative Experience

Though all cases vary and none is predictive, David’s experience includes:

Tax Controversies and Investigations

  • Prosecuting, on behalf of multiple clients, petitions in U.S. Tax Court challenging tax deficiencies asserted by the IRS.
  • Defending the chairman of an investment firm in a DOJ criminal tax investigation.
  • Representing multiple taxpayers in an IRS audit of conservation easements.

Patent and Intellectual Property Litigation

  • Prosecuting, through a multi-week trial in the District of New Jersey, a branded pharmaceutical company’s patent-infringement claims.
  • Prosecuting patent infringement claims on behalf of Alcon, now a division of Novartis, in multiple cases in the District of Delaware relating to Alcon’s Travatan Z, Ilevro, and Izba products.
  • Prosecuting a branded pharmaceutical company’s patent infringement claims in federal multi-district litigation against over a dozen generics.

Food and Beverage Litigation

  • Defending a packaged-food manufacturer in a consumer class-action lawsuit in the District of Massachusetts.  The district court dismissed the complaint with prejudice, and the First Circuit affirmed the decision on appeal.
  • Defending multiple packaged-food manufacturers in California consumer class-action lawsuits alleging misleading labeling.
  • Defending a packaged-food manufacturer in a California lawsuit seeking relief from plastic pollution.

Other Experience

  • Representing the chief executive of a global auto industry manufacturer in a DOJ criminal fraud investigation.
  • Representing a trader at a major bank in an SEC securities fraud investigation.
  • Representing testifying witnesses in multiple federal criminal prosecutions.
  • Prosecuting, through trial, a public company’s claims that the District of Columbia breached a government contract for provision of technology.
  • Prosecuting, through a commercial arbitration hearing, a financial services firm’s claims seeking damages for breach of a data-provision contract.
  • Prosecuting, pro bono, an individual client’s successful appeal from a conviction for second-degree assault.
  • Representing an individual client in the U.S. Supreme Court in an appeal addressing the constitutionality of DNA swabbing at the time of arrest (Maryland v. King).




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