Karen Otto’s antitrust practice includes assisting clients with government reviews of mergers and acquisitions, civil antitrust litigation, government investigations, and counseling in relation to antitrust issues. Ms. Otto also has counseled clients and prepared regulatory filings for transactions under the Hart-Scott-Rodino Act.

Prior to joining Arnold & Porter, Ms. Otto served as a law clerk to the Honorable Stanley Marcus of the United States Court of Appeals for the Eleventh Circuit.

Ms. Otto graduated first in her class from the Duke University School of Law, where she was an Executive Editor of the Duke Law Journal and a Mordecai Scholar. Prior to law school, Ms. Otto received a master's degree in economics from Georgetown University. She earned her bachelor's degree in mathematics and economics with distinction from the University of Virginia, graduating Phi Beta Kappa.


  • Global payment card company in federal antitrust multidistrict litigation challenging interchange fees and other practices.
  • Global payment card company in federal antitrust class action litigation challenging ATM access fees.
  • AT&T Inc. in its acquisitions of DIRECTV and Leap Wireless.


  • JD, Duke University School of Law, 2011, summa cum laude, Order of the Coif
  • MA, Georgetown University, 2006
  • BA, University of Virginia, 2004, with distinction, Phi Beta Kappa
  • District of Columbia
  • US Court of Appeals for the Fifth Circuit
  • United States Court of Appeals, Eleventh Circuit, The Honorable Stanley Marcus
  • Spanish

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