Kitty Genovese was murdered in New York City, prompting research into the bystander effect due to the false story that neighbors witnessed the killing and did nothing to help her.

In the early hours of March 13, 1964, Kitty Genovese, a 28-year-old bartender, was raped and stabbed to death outside the apartment building where she lived in the Kew Gardens neighborhood of the Queens borough of New York City, United States. Two weeks after the murder, The New York Times published an article claiming that thirty-seven witnesses saw or heard the attack, and that none of them called the police or came to her aid. However, subsequent investigations revealed that the extent of public apathy was exaggerated. While some neighbors heard her cries, many did not realize the severity of the situation. The incident prompted inquiries into what became known as the bystander effect, or "Genovese syndrome", and the murder became a staple of U.S. psychology textbooks for the next four decades.

The bystander effect, or bystander apathy, is a social psychological theory that states that individuals are less likely to offer help to a victim in the presence of other people. The theory was first proposed in 1964 after the murder of Kitty Genovese, in which a newspaper had reported that 37 bystanders saw or heard the attack without coming to her assistance or calling the police. Much research, mostly in psychology research laboratories, has focused on increasingly varied factors, such as the number of bystanders, ambiguity, group cohesiveness, and diffusion of responsibility that reinforces mutual denial. If a single individual is asked to complete a task alone, the sense of responsibility will be strong, and there will be a positive response; however, if a group is required to complete a task together, each individual in the group will have a weak sense of responsibility, and will often shrink back in the face of difficulties or responsibilities.