A handwriting expert initially suggested that Van Best Jr.'s writing on a marriage certificate matched the Zodiac's cryptic letters.
Van Best Jr. was a convicted pedophile with a history of predatory behavior, providing a psychological profile that Stewart argued fit the killer. The FX Docuseries and Debunking
After being contacted by his birth mother at age 39, Stewart began investigating his biological father, . Stewart claims that Van Best Jr. is the Zodiac Killer based on several pieces of circumstantial evidence:
Stewart noted a striking similarity between his father's mugshot and the 1969 police sketch of the Zodiac.