At the urging of
Governor Whitman he unsuccessfully prosecuted the Warden of
Sing Sing prison
Thomas Osborne on trumped up charges, including "Gross Immorality" with prisoners because the Governor wished to be rid of a prison reformer whom he considered too soft. In 1918 he set up a law firm with his friend,
Eugene F. McGee; it was around this time that he met Arnold Rothstein who was taken by the polished charm of the lawyer who was known for his oratory skills taught to him during his Jesuit education and his reputed photographic memory that allowed him to memorize whole books in hours. During the Black Sox Trial Fallon had a falling out with his client Nicky Arnstein because of his noticeable heavy drinking. Arnstein fired Fallon and was later found guilty. Afterward Fallon defended many White Collar criminals involved with stock fraud, his tendency to get hung juries attracted the attention of muckrakers and in 1924 he was tried and acquitted for jury tampering. However, his reputation was damaged and his career never recovered. He was also prosecuted in the
Fuller case. ==Death and legacy==