An amateur sleuth and self-taught cryptography expert is convinced he’s cracked the notorious unsolved Zodiac and Black Dahlia murders — and that the killer is the same man. Alex Baber — a 50-year-old West Virginian with autism — used AI programs and his codebreaking prowess to whittle down the Zodiac killer’s infamous 1970 clue he sent to newspapers and identify a single suspect with an overwhelming connection across all the murders: a late Chicagoan named Marvin Margolis. “It’s my autism. Once I start on something, I have to see it through. The deeper I go, the harder I push. My...