Between December 1968 and October 1969, an unidentified assailant calling himself the Zodiac Killer murdered at least five people and wounded two others in Northern California. He attacked couples parked in their cars and a San Francisco taxi driver, then sent taunting letters and ciphers to newspapers. Despite intensive investigation, the killer was never identified and the case remains unsolved.

A serial rapist and murderer known as the Golden State Killer committed more than 120 burglaries, at least 45 rapes and 13 murders across California during the 1970s and 1980s. Former police officer Joseph James DeAngelo eluded detection for decades until genetic genealogy identified him in 2018. In June 2020 he pleaded guilty to 13 murders and kidnappings in a multi‑county plea deal and was sentenced to consecutive life sentences without parole.

On Jan. 15 1947, 22‑year‑old Elizabeth Short's mutilated body was found in a vacant lot near Leimert Park in Los Angeles. Her body had been severed and drained of blood, and the Los Angeles Police Department never arrested anyone. The sensationalized slaying, dubbed the "Black Dahlia" murder, remains one of the city's oldest unsolved homicides.

On July 18 1989, 21‑year‑old actress Rebecca Schaeffer was shot and killed at her Los Angeles apartment by Robert John Bardo, an obsessed fan who had obtained her address from a private investigator. Her slaying spurred California to pass anti‑stalking legislation and restrict access to DMV records. Bardo was arrested the next day, prosecuted by the Los Angeles County district attorney and, in 1991, convicted of capital murder and sentenced to life in prison without parole.

On Aug. 20 1989, brothers Lyle and Erik Menendez shot their parents, entertainment executive José Menendez and his wife Mary "Kitty" Menendez, at their Beverly Hills mansion. They initially claimed intruders committed the crime but later argued they acted after years of abuse. A 1995–96 retrial ended with convictions for first‑degree murder and life sentences; in 2025 a judge resentenced them to 50 years to life but they remain imprisoned.