Samuel A. Adams, a one-time CIA analyst who accused his superiors of manipulating intelligence estimates during the Vietnam War, has died. He was 55.

Adams, whose accusations helped form the basis of the CBS-Westmoreland libel case, died Monday at his home in Strafford, apparently of a heart attack.Adams was a CIA expert on the Viet Cong, the guerrilla force that North Vietnam organized in South Vietnam. He contended that Army Gen. William Westmoreland's military intelligence officers were ordered to deliberately underestimate the strength of the guerrilla force to make it appear the American-backed war was being won.

The dispute over the Viet Cong strength was a major controversy at the CIA, where Adams worked for 10 years. It became the basis for the 1982 CBS documentary, "The Uncounted Enemy: A Vietnam Deception," which resulted in a libel suit against the network by Westmoreland.