Media item displaying Atticus DeProspo

Atticus DeProspo

Associate

[email protected]

202.434.5861

Atticus DeProspo’s practice focuses on complex civil and criminal litigation at the trial and appellate levels as well as government investigations. He has represented individuals and corporate clients in high-stakes matters in federal and state courts around the country, including as merits counsel in the U.S. Supreme Court. Atticus has argued before the U.S. Court of Appeals for the Seventh Circuit, U.S. Court of Appeals for the Eighth Circuit, the U.S. District Court for the District of Utah, and the Appellate Court of Maryland.  Atticus has taken and defended depositions, conducted a direct examination at a hearing, and worked extensively with fact and expert witnesses to prepare them to testify at trial and arbitration.  He also maintains an active pro bono practice and leads the firm’s “Making Justice Real” campaign to support D.C. Legal Aid for which he was named Young Lawyer of the Year by the Bar Association for the District of Columbia in December 2025.

He has experience in a broad range of substantive areas, including sports law, administrative law, criminal law, federal statutory interpretation, separation-of-powers questions, First Amendment, state consumer protection laws, antitrust, and contract law. Atticus has litigated cases against the Consumer Financial Protection Bureau, State Attorneys General, the federal government, state governments, and major corporations. 

Atticus has also guided major corporations and senior corporate executives through intense and highly sensitive matters, in government investigations.  Notably, Atticus has represented a Fortune 500 healthcare company that provides government-sponsored and commercial healthcare programs through various government investigations.  This includes in government investigations, where a resolution was reached prior to a complaint being filed or criminal charges being brought. 

Atticus DeProspo joined Williams & Connolly as an associate in 2021. Before joining the firm, Atticus clerked for Judge Steven J. Menashi of the United States Court of Appeals for the Second Circuit and for Chief Judge L. Scott Coogler of the United States District Court for the Northern District of Alabama.

Atticus received his B.S. in Industrial and Labor Relations with honors, highest distinction, from Cornell University. He was a four-year member of the Cornell Varsity Men’s Soccer Team, where he helped them win the Ivy League Championship in 2012. Atticus interned in Florida and Washington, D.C. for Senator Marco Rubio. He also served as an intern at the Supreme Court of the United States for Justice Sonia Sotomayor. Atticus was selected as a member of the inaugural class of the Schwarzman Scholars Program, where he received his M.S. in Global Affairs from Tsinghua University. Atticus was also selected as a Gates-Cambridge Scholar, where he graduated with an M.Phil. in Criminology from the University of Cambridge. He received his J.D. magna cum laude and Order of the Coif from the University of Alabama School of Law, where he served as an editor on the Alabama Law Review. 

Experience

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

TRIAL & GOVERNMENT INVESTIGATIONS EXPERIENCE:

  • Successfully obtained a civil protective order for a client in D.C. Superior Court, which included conducting a direct examination of a witness at the civil protective order hearing
  • Representation of the two largest credit repair organizations in the United States in a lawsuit filed by the CFPB involving alleged violations of TSR and CFPA relating to credit repair services provided to consumers, which included successfully arguing a Daubert motion to exclude the CFPB’s expert witness on chargeback data in federal district court
  • Lead mediation counsel for an employee that successfully resulted in a six-figure global settlement for wrongful discharge, retaliation, and discrimination claims
  • Investigations counsel for a Fortune 500 healthcare company in several State agency investigations regarding allegations of surveillance of State lawmakers, which included leading interviews of senior executives
  • Arbitration counsel of former NFL coach in a contract dispute with an NFL Team before an arbitrator appointed by the NFL Commissioner, which included deposing the NFL Team’s Head of Human Resources
  • Trial counsel for a Fortune 500 biotechnology company in a breach of contract damages bench trial
  • Investigations counsel for a financial services company that offers personal and auto loans to individuals with limited access to traditional lenders in State Attorneys General investigations regarding Guaranteed Asset Protection insurance policies
  • Investigations counsel of one of the largest accounting firms in an SEC investigation regarding independence rules
  • Representation of a Fortune 500 healthcare company in a wrongful death and survivor action in State court involving claims for negligence, insurance fraud, consumer fraud, and breach of contract
  • Representation of inventors and manufacturers of medicines against antitrust, trade secret claims, and breach of contract claims brought by competitors, ensuring that patients have reliable access to innovative treatments
  • Representation of a major news organization in a lawsuit alleging claims for an invasion of privacy, negligence, wantonness, and intentional infliction of emotional distress under Alabama law
  • Representation of one of the largest pharmacy benefit managers and its related entities in lawsuits filed by State Attorneys General, cities, counties, and unions in multiple jurisdictions throughout the United States involving alleged violations of RICO, state consumer protection laws as well claims for unjust enrichment and civil conspiracy in connection with insulin pricing

APPELLATE EXPERIENCE:

  • Merits counsel in the U.S. Supreme Court, which held unanimously that restitution under the Mandatory Victims Restitution Act is criminal punishment for purposes of the U.S. Constitution’s Ex Post Facto Clause in Ellingburg v. United States, Case No. 24-482
  • Successfully petition the U.S. Supreme Court to grant a petition for a writ of certiorari in United States v. Ellingburg, Case No. 24-482
  • Argued and briefed appeal as court-appointed counsel on behalf of a criminal defendant in the U.S. Court of Appeals for the Eighth Circuit regarding whether applying the Mandatory Victim Restitution Act to a criminal defendant’s restitution order as to the liability period or the collection of interest would violate the Ex Post Facto Clause of Article I, Section 9 of the U.S. Constitution
  • Argued and briefed appeal on behalf of a criminal defendant in the U.S. Court of Appeals for the Seventh Circuit regarding whether “loss” in § 2B1.1 of the Sentencing Guidelines is genuinely ambiguous after applying the U.S. Supreme Court’s step-by-step analysis in Kisor v. Wilkie
  • Authored amicus brief at the merits stage in the U.S. Supreme Court on behalf of a national trade association of leading e-commerce and online businesses regarding property-based bailment principles under the Fourth Amendment in Chatrie v. United States, Case No. 25-112
  • Appellate counsel in the Idaho Supreme Court, which held unanimously that: (1) a competitor’s four non-constitutional claims were a request for a judicial review expressly prohibited by the State Procurement Act; (2) a writ of mandate was not appropriate under the circumstances; (3) the State Procurement Act’s restrictions on judicial review did not violate the separation of powers doctrine under the Idaho Constitution; and (3) Idaho Code Section 67-9230(8) is not void for vagueness under the Due Process Clause of the U.S. Constitution
  • Briefed appeal in support of a petitioner in the U.S. Court of Appeals for the Third Circuit regarding whether the Board of Immigration Appeals abused its discretion in denying petitioner’s motion to reopen by failing to full consider petitioner’s evidence of changed country conditions
  • Briefed appeal on behalf of a criminal defendant in the U.S. Court of Appeals for the Eleventh Circuit regarding the constitutionality of Section 922(g)(1) after applying the Supreme Court’s Second Amendment analysis in Rahimi v. United States and whether police lacked reasonable suspicion to extend a traffic stop in order to conduct a dog sniff in violation of the Fourth Amendment
  • Briefed appeal for a Fortune 500 biotechnology company in the U.S. Court of Appeals for the Third Circuit involving claims for antitrust violations and breach of contract as well as erroneous evidentiary rulings and unsupportable damages awards
  • Argued and briefed on behalf of a criminal defendant in the Appellate Court of Maryland regarding whether a criminal defendant waived his right to a jury trial knowingly and voluntarily
  • Briefed appeal on behalf of NFL Player and Super Bowl Champion in a contract dispute with his former agent over an endorsement deal in the New York Court of Appeals
  • Briefed appeal in the Hawaii Supreme Court on behalf of amicus curiae involving alleged violations of Hawaii’s Unfair or Deceptive Acts or Practices law by pharmaceutical companies about warning labels for consumers of Plavix

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