In what a Long Island judge said was “at its bitter core, a Greek tragedy,” the son, who is a former associate of a suspended attorney, has convinced the court that his father is not entitled to $2,600 in unpaid rent from a subtenant who is now the son’s partner.

The suspended lawyer, Sheldon M. Krupnick, of Garden City, said in an interview after an unusual five-day small claims trial that he had not expected his son, Kevin P. Krupnick, to stand up against him in court, but noted that there had been previous problems between him and his son, whom he did not hesitate to call as an adverse witness.