

Margo R. Casselman
- Phoenix
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Margo assists clients, from individuals and privately held firms to Fortune 500 public companies, with high-stakes, complex litigation and dispute resolution.
From prelitigation through trial and appeal, Margo Casselman has litigated a range of contract and other commercial disputes, business torts, cases involving constitutional and other governmental issues, election law cases, intellectual property disputes, and employment-related disputes. As a member of the firm’s White Collar & Investigations practice, Margo also has experience defending individuals and businesses against criminal and other government investigations at the federal and state levels. She also regularly represents clients in arbitrations and other alternative dispute resolution proceedings.
Margo has significant courtroom experience. Margo’s recent courtroom successes include briefing and arguing a motion to dismiss in federal court resulting in the grant of dismissal of claims with prejudice; cold examinations of witnesses in state and federal court during trial or preliminary injunction hearings; delivering the opening statement and examining a witness at an evidentiary hearing resulting in dismissal of a lawsuit; and leading a settlement conference before a U.S. magistrate judge in a federal civil rights case that ultimately settled favorably on the eve of trial.
Before joining the firm, Margo clerked for the Honorable David G. Campbell of the U.S. District Court for the District of Arizona and the Honorable Mary H. Murguia of the U.S. Court of Appeals for the Ninth Circuit.
Margo also maintains an active pro bono practice. She has litigated Section 1983 constitutional claims to secure medical care and humane conditions for persons affected by the justice system.
Areas of focus
Education & Credentials
Education
- University of Arizona James E. Rogers College of Law, J.D., Order of the Coif, Articles Editor, Arizona Law Review, 2017
- Arizona State University, B.A., Business, summa cum laude, Certificate in International Business, 2014
Bar and Court Admissions
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Arizona
- Supreme Court of the United States
- Supreme Court of Arizona
- U.S. Court of Appeals for the Ninth Circuit
- U.S. District Court for the District of Arizona
Clerkships
- Hon. Mary H. Murguia, U.S. Court of Appeals for the Ninth Circuit
- Hon. David G. Campbell, U.S. District Court for the District of Arizona
Professional Recognition
Listed as a "Southwest Rising Star" by Super Lawyers, 2022-2025