Keenan was in private practice of law in New York City in 1956. He was an assistant district attorney of New York County from 1956 to 1976.[2] He was an assistant district attorney in charge of Supreme Court Bureau of New York County from 1968 to 1969. He was an assistant district attorney in charge of homicide bureau in New York County from 1970 to 1973. He was the chief assistant district attorney of Queens County in 1973. He was an administrative assistant district attorney in charge of trials in New York County in 1974. He was the chief assistant district attorney of New York County from 1974 to 1976. He was a deputy state attorney general/special prosecutor of corruption in New York City from 1976 to 1979.[2]
He was the Chairman and President of New York City Off-Track Betting Corporation from 1979 to 1982. He was the criminal justice coordinator of New York City from 1982 to 1983. He was a member of the Republican Party.[3][4][5]
His rulings include authorizing the publication of Jeffrey Toobin's Opening Arguments, an account of the Iran–Contra affair, over the objections and threat of prosecution by Lawrence E. Walsh;[7] managing the delivery of medical relief funds to India following the Union Carbide Corporationgas plant disaster in Bhopal[8] and dismissing attempts to sue Union Carbide in U.S. courts rather than in India;[9] denying a gay Irish group the right to hold its own march on the same day as the city's St. Patrick's Day parade in 1995, determining that the city's claims that it would pose a safety hazard trumped the group's First Amendment claims.[10] He presided at the trial of Bess Myerson, New York City Cultural Affairs Commissioner, on corruption charges in 1988[11] and that of Philippine first lady Imelda Marcos on racketeering charges in 1990.[12]
Reversed cases
On August 16, 2010, Keenan sentenced Mahmoud Reza Banki to 30 months in prison.[13] This sentence was overturned on October 24, 2011, at which time the United States Court of Appeals for the Second Circuit ruled in favor of Banki reversing the sanctions charges against him.[14] Appellate court ruled that Judge John F. Keenan had erred at trial; in denying Banki's defense request to instruct the jury on the law that specifically exempts family money as an exception to the sanctions law, permitting such transfers without the need for a license. The final appellate court brief stated: "Banki's conviction [on the sanctions charges] cannot stand".[15]
Personal life and death
In 1956, Keenan married Diane Nicholson, and they had a daughter.[2] He died at his home in the Bronx on October 27, 2024, at the age of 94.[2][16]