A juicy new documentary about the life and public battles of late real estate mogul Leona Helmsley is currently in production, Variety has learned exclusively. The film will contain never-before-heard tapes of Helmsley and her archrival Donald Trump, as well as “smoking gun” evidence that will question the tax evasion case brought on her by Rudy Giuliani in 1988.

Helmsley was an icon of the “greed is good” era, an owner of luxury hotels and condominiums who left behind a 5 billion estate. Branded the “Queen of Mean” by the New York tabloids for her acid tongue and regal air, she was a bitter rival of Trump — who once called her “a disgrace to the industry and a disgrace to humanity in general.” Of Trump, Helmsley once reportedly said: “I wouldn’t trust him if his tongue was notarized.”

Trump notoriously tried to snatch the crown jewel of Helmsley’s property portfolio,...