Professor Karl has published widely on comparative politics and international relations, with special emphasis on the politics of oil-exporting countries, transitions to democracy, problems of inequality, the global politics of human rights, and the resolution of civil wars. She has conducted field research throughout Latin America, West Africa and Eastern Europe. Her work has been translated into 15 languages.
Karl has been an expert witness in major human rights and war crimes trials in the United States that have set important legal precedents, most notably the first jury verdict in U.S. history against military commanders for murder and torture under the doctrine of command responsibility and the first jury verdict in U.S. history finding commanders responsible for "crimes against humanity" under the doctrine of command responsibility. In January 2006, her testimony formed the basis for a landmark victory for human rights on the statute of limitations issue. As a result of her human rights work, she received the Doctor of Humane Letters, honoris causa from the University of San Francisco in 2005.
Professor Karl has been recognized for "exceptional teaching throughout her career," resulting in her appointment as the William R. and Gretchen Kimball University Fellowship. She has also won the Dean's Award for Excellence in Teaching (1989), the Allan V. Cox Medal for Faculty Excellence Fostering Undergraduate Research (1994), and the Walter J. Gores Award for Excellence in Graduate and Undergraduate Teaching (1997), the University's highest academic prize. Karl served as director of Stanford's Center for Latin American Studies from 1990-2001, was praised by the president of Stanford for elevating the Center for Latin American Studies to "unprecedented levels of intelligent, dynamic, cross-disciplinary activity and public service in literature, arts, social sciences, and professions." In 1997 she was awarded the Rio Branco Prize by the President of Brazil, Fernando Henrique Cardoso, in recognition for her service in fostering academic relations between the United States and Latin America.