The Onion Field is a 1973 nonfiction book by Joseph Wambaugh, a sergeant for the Los Angeles Police Department, chronicling the kidnapping of two plainclothes LAPD officers by a pair of criminals during an evening traffic stop and the subsequent murder of Officer Ian James Campbell. It was one of the most influential murder cases in U.S. history, as it forced the Los Angeles Police Department and other large municipalities to change some of their police tactics in the field.