Paul Bernardo, dubbed the “Scarborough Rapist,” sexually assaulted at least 18 women between May 4, 1987, and April 6, 1991.

During his formative years, Bernardo had begun to display signs of scoptophilia, peeping through windows at young women to achieve sexual gratification. At the age of 16, his mother, Marilyn Bernardo, informed him that Kenneth Bernardo was not his father; the boy was the product of an illicit affair with a prominent businessperson. Following this, the distance between Bernardo and his parents increased, as did his aggressive behavior toward women. On completion of a bachelor's degree in commerce and unable to find full-time employment as an accountant, Bernardo began to smuggle cigarettes across the border.

Karla Homolka spent her formative years in a lower-middle-class suburb in St. ...