David Horniak litigates complex, high-stakes civil and criminal cases around the country at both the trial and appellate levels. He has successfully represented clients in a broad range of substantive areas of litigation, with a particular emphasis on investigations and litigation brought by federal and state criminal, securities, and tax authorities; legal malpractice defense; intellectual property litigation; and consumer class action defense. David has guided clients through investigations and litigation brought by the IRS, SEC, CFTC, DOJ, and state attorneys general; defended global law firms facing complex, multi-jurisdictional legal malpractice claims; prosecuted and defended pharmaceutical patent infringement actions and inter partes review proceedings; and defended food manufacturers in numerous class actions brought under state and federal consumer-protection laws. He has argued numerous motions, taken and defended countless depositions, 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.
David represents a broad range of clients, from individuals and start-ups to Fortune 500 corporations and global law firms. To his clients, David is not only a forceful advocate, but also a trusted advisor. As reported by The Legal 500, clients describe him as “easily accessible” and “respectful,” someone who “quickly responds to client inquiries with direct and helpful communication.” He “always tak[es] the time needed to ensure in-house counsel are up-to-speed and understanding of the process and issues.” 

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:

Government Investigations and Litigation

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

 Legal Malpractice

  • Defending multiple global law firms against allegations of legal malpractice and related claims.

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.
  • Defending inter partes review petitions challenging patents covering a novel cancer therapy.

Consumer Class Action Defense

  • Defending a pet-food manufacturer in multiple consumer class action lawsuits in the Southern District of Florida.  The district court dismissed the complaints with prejudice.
  • 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 a fast-food franchise in California consumer class-action lawsuits and arbitrations alleging false advertising.
  • Defending multiple packaged-food manufacturers in California consumer class-action lawsuits alleging misleading labeling.

Other Experience

  • 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.




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