Former Nassau County District Attorney Denis Dillon, who in more than three decades on the job prosecuted numerous high-profile defendants ranging from Long Island Lolita Amy Fisher to the gunman in the 1993 Long Island Rail Road massacre, died Sunday from lymphoma at his home in Rockville Centre. He was 76.

Longtime spokesman Ed Grilli said Mr. Dillon worked as a top-notch prosecutor, not as a politician, achieving one of the highest felony conviction rates in the country.