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40 & Under Hot List

Litigation Star

Practice area:


A former clerk for Justice Antonin Scalia and, before that, for Judge Diarmuid F. O’Scannlain on the Ninth Circuit, Daniel Sullivan has been recognized as a Rising Star (2015) and a Trailblazer (2020) by the New York Law Journal, and an Elite Boutique Trailblazer (2020) by The National Law Journal. He has also been named to Benchmark Litigation’s Under 40 Hot List since 2017 and as a Future Star since 2018.

A leader of Holwell Shuster & Goldberg’s appellate practice, Dan has represented clients in a broad range of matters. Recent wins include: a reversal of a jury verdict in New York’s First Department in an appeal establishing an important precedent in asbestos cases; a First Department opinion holding, on a novel legal question, that $140 million in SEC disgorgement is not insurable as a penalty; and a reversal in the Federal Circuit of a jury trial judgment in a patent-infringement case against an auto-parts manufacturer. In January 2021, he won an order from the U.S. Supreme Court vacating a Second Circuit decision in an appeal with significant implications for insider trading prosecutions. He is presently representing TIG Insurance Company in an appeal in the Second Circuit addressing when an ADR provision requires subsequent agreement to use arbitration in order to be enforceable.

In a matter Dan handled in his individual capacity, he represented Senator Ted Cruz in ballot eligibility challenges in New York State and federal court in connection with the 2016 Republican Presidential Primary election, prevailing in every case. 

Simultaneously, he has a leading role in trial-level commercial litigation. This includes representing trustees in massive RMBS putback cases covering billions of dollars in loans, including two cases against Nomura where summary judgment is currently being briefed; leading, with Mike Shuster and Blair Kaminsky, HSG’s representation of the Chubb family of insurers in all insurance coverage disputes arising out of the opioid crisis—currently in state and federal courts around the country including California, Delaware, Ohio, and West Virginia; securities fraud matters; and other business litigation. Dan also represented minority partners and management of a Puerto Rican auto-loan servicing business in a contentious partnership dispute with a prominent hedge fund. Dan led the HSG team that took over the case after an adverse partial summary-judgment ruling; HSG initiated new litigation in Puerto Rico federal court, argued and won several key motions in the pending New York action, and fought what became a sprawling case across three fora. The case ultimately settled favorably. 

Dan is also an active member of HSG’s pro bono practice, especially in immigration appeals. In two recent cases in federal circuit courts, he represented legal permanent residents under orders of removal in appeals raising novel legal questions. In both, after Dan filed his opening brief, the government agreed to a favorable remand. 

Key Practice Areas:

  • Appellate
  • Business & Commercial
  • Civil Litigation
  • Class Action
  • Constitutional
  • Intellectual Property
  • Securities

Year Joined Firm:


  • The University of Chicago Law School (J.D., Order of the Coif)
  • The University of Chicago (B.A.)


Updated Sep 2021