The film was based on the murder of Kirsten Costas. On June 23, 1984, in Orinda, California, Costas was murdered by her classmate, Bernadette Protti. Protti had been jealous of Costas, who was the daughter of affluent parents and very popular at Miramonte High School. Kirsten had been a member of the yearbook committee and a cheerleader. However, Bernadette was not accepted by the yearbook committee and tried out for cheerleading, but was not picked. Kirsten, who was chosen to be a cheerleader, saw Bernadette as a wannabe and didn't take her seriously.