The Zodiac killer operated in Northern California in the late 1960s, killing at least five people. Some of the victims included high school sweethearts David Faraday and Betty Lou Jensen, as well as taxi driver Paul Stine. The killer taunted police with ciphers and letters and was never identified. Crime scenes were processed using techniques like triangulation, baselines, and polar coordinates to map evidence and recreate the crimes. The Zodiac killer remains one of the most infamous unsolved serial murder cases.