Nesson rose to fame by defending Daniel Ellsberg, who in 1971 leaked to the media the "Pentagon Papers," secret documents that indicated the government deceived the public about whether the Vietnam War could be won. Ellsberg faced up to 115 years in prison, but the charges were dismissed because of government misconduct against him.
Later, attorney Jan Schlichtmann persuaded Nesson, an expert in evidence, to join his legal fight against chemical companies whose alleged polluting was suspected of causing leukemia among children in Woburn. Jonathan Harr's book, "A Civil Action," documented the case and was later turned into a film starring John Travolta.