Lorenson is a graduate of MIT. In the early 1990s, she spent several years teaching English and doing translation and secretarial work for human rights organizations in Nicaragua and El Salvador. Later, she worked as a freelance journalist while traveling in Peru.
On November 30, 1995, Berenson was arrested on a public bus in downtown Lima, the capital of Peru, accused of collaborating with an insurgent organization, the Movimiento Revolucionaro Túpac Amaru (MRTA). Anti-terrorist police accused Berenson of providing MRTA with detailed information on the floor plans of the Congress, its security and members, and that she rented an apartment and a house for them to use.
The police claimed that diagrams, notes, weapons and police and military uniforms found at the safe house suggested that the group was planning to seize members of Congress and trade them for captured guerrillas. Berenson's lawyers argued that she had no prior knowledge of the planned attack, and that she believed that the information she gathered for an article on the Peruvian Congress would be used by the guerrillas to form a political party. A hooded military tribunal, using anti-terrorism legislation promulgated during a state of emergency declared by Peruvian president Alberto Fujimori, sentenced her to life in prison for "treason against the fatherland."
In April 1998, Amnesty International issued a press release declaring Berenson to be a political prisoner. Amnesty criticized the Peruvian anti-terrorism legislation, stating that "it is unacceptable for hundreds of political prisoners like Berenson not to be able to exercise their basic human right to a fair and public hearing by an independent and impartial tribunal." In the spring of 2001, due to international pressure, her sentence was vacated and she was retried by a civilian court under the same anti-terrorism legislation. The original verdict was upheld, but Berenson's sentence was reduced to twenty years.
When U.S. president George W. Bush travelled to Peru in April 2002 to meet with Peruvian president Alejandro Toledo, there was pressure on him to search for a humantarian solution to Berensen's situation, but Bush's firm avowal of a "war on terrorism" left little likelihood of him arguing on behalf of an American accused of terrorism abroad. The Peruvian public, shell-shocked from fifteen years of violence, likewise has little sympathy for anyone connected to terrorism and appears indifferent to her case.