Hayes became a licensed attorney in New York in 1973 and worked as an Assistant District Attorney in the homicide unit in
the Bronx before opening a private practice. In the matter of the Warhol estate, Hayes was hired by the artist's foundation for a fee proportional to the value of the estate. His appraisers valued the estate at nearly $700 million, in contrast to the $100 million figure that
Christie's auction house had given the foundation. The Court found the estate was worth $500 million. The Foundation is required to give away 5% of the value of its assets, so this decision was important to the public, as well as to Hayes. After several rounds of litigation between Hayes and the Foundation, an Appellate Court ruled he had been overpaid, violated his fiduciary duties to the Estate and owed them over a million dollars. On August 23, 1996, Hayes filed for bankruptcy according to the Second Circuit's opinion in the case. Hayes filed a complaint against the Appellate Judge who ruled against him, Justice Francis Murphy, on the grounds that Murphy had a relationship with the lawyer for the Foundation that he should have disclosed. Murphy resigned rather than answering the complaint. In the 2000s, Hayes collaborated with
Bruce Cutler, best known as
John Gotti's former attorney, in defending a pair of New York police officers accused of organized crime related murders. At this time, Hayes also represented Daniel Libeskind, the master plan architect for the reconstruction of the World Trade Center site in Lower Manhattan. ==Pop culture==