Concurrently, as chairman of the board of editors of the Research Institute of America (1938–1949),[6] Casey initially conceptualized the tax shelter and "explained to businessmen how little they need[ed] to do in order to stay on the right side of New Deal regulatory legislation.

"[7] During World War II, he worked for the Office of Strategic Services, where he became head of its Secret Intelligence Branch in Europe.

[4][8] He served in the United States Naval Reserve until December 1944 before remaining in his OSS position as a civilian until his resignation in September 1945; as an officer, he attained the rank of lieutenant and was awarded the Bronze Star Medal for meritorious achievement.

[10] He served in the Nixon administration as the chairman of the Securities and Exchange Commission from 1971 to 1973;[4][11] this position led to his being called as a prosecution witness against former Attorney General John N. Mitchell and former Commerce Secretary Maurice Stans in an influence-peddling case stemming from international financier Robert Vesco's $200,000 contribution to the Nixon reelection campaign.

Casey would fail to disclose his legal clients and finances from the 1970s to the U.S. Senate during his confirmation hearings to become Director of Central Intelligence.

During the trip, Connally asked Arab leaders to convey to the Iranian government that Iran should wait to release American hostages until after the election of 1980 was concluded.

Barnes claimed that Casey discussed with Connally if the Iranians "were going to hold the hostages," possibly corroborating the October Surprise theory.

[35] Despite Casey's background in intelligence, the position was not his first choice; according to Rhoda Koenig, he only agreed to take the appointment after being assured that "he could have a hand in shaping foreign policy rather than simply reporting the data on which it was based.

[36] Ronald Reagan used prominent Catholics in his government to brief Pope John Paul II of developments in the Cold War.

During his tenure, post-Watergate and Church Committee restrictions were controversially lifted on the use of the CIA to directly and covertly influence the internal and foreign affairs of countries relevant to American policy.

"[39] In his final report (submitted in August 1993), Independent Counsel Lawrence E. Walsh indicated evidence of Casey's involvement: There is evidence that Casey played a role as a Cabinet-level advocate both in setting up the covert network to resupply the contras during the Boland funding cut-off, and in promoting the secret arms sales to Iran in 1985 and 1986.

[4] However, Walsh also wrote: "Independent Counsel obtained no documentary evidence showing Casey knew about or approved the diversion.

[45] In 1948, he purchased Locust Knoll, an 8.2 acres (3.3 ha) North Shore estate centered around a main 1854 Jacobethan house in Roslyn Harbor, New York, for $50,000.

Daniel Fagan, then pastor of St. Mary's Roman Catholic Church in Roslyn, New York, and his funeral was led by Bishop John R. McGann, who used his pulpit to castigate Casey for his ethics and actions in Nicaragua.