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

  • Representing multiple individual clients in ongoing U.S. Tax Court proceedings 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

  • Representing a pharmaceutical company in patent litigation in the District of New Jersey.  The representation included a multi-week trial in the second half of 2019.     
  • Representing Alcon, now a division of Novartis, in patent litigation in the District of Delaware relating to Alcon’s Travatan Z, Ilevro, and Izba products. 

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 decision is now on appeal.
  • Defending multiple packaged-food manufacturers in California consumer class-action lawsuits alleging misleading labeling.

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, through trial, a public company suing the District of Columbia for breaching a government contract for provision of technology.
  • Representing, in commercial arbitration, a financial services firm seeking damages for breach of a data-provision contract.
  • Representing, pro bono, an individual client in a successful appeal from a conviction for second-degree assault.
  • Representing an individual client in an appeal to the United States Supreme Court.




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