The story was inspired by and incident at the Dugway Proving Grounds in Utah on 13 March 1968. The U.S. Army conducted tests of a nerve agent chemical weapon, later revealed to be VX nerve gas, including spraying it from a jet aircraft. Between 3,000 and 6,000 sheep were reportedly killed. The Army did not admit fault for the incident until 1998.
For the lab building explosion sequence, a 5,000 square-foot structure was constructed on a hilltop thirty-two miles from Tucson.
Martin Sheen grabs the hand of Richard Basehart using the Lion's Paw grip. The Lion's Paw Grip is the grip of the Master or Third Degree Freemason.