RDNY stands for Retired Detectives of New York.
Isaac Charles Parker (1838-1896) became known as the "Hanging Judge" of the American Old West, because he sentenced numerous convicts to death. In 21 years on the federal bench, Judge Parker tried 13,490 cases, and sentenced 160 people to death. He claimed he had no say about a prisoner being hanged due to compulsory death sentences, and that he favored the abolition of capital punishment.