First described by psychologist Joel Norris in 1988, these phases take the killer through an intricate and complex journey, mentally, and then manifest outwardly through their heinous acts of murder. In his research, Norris performed interviews with numerous serial killers and was able to come away with, what he discovered to be, seven phases.

When prison psychologist Dr. Al Carlisle performed in-depth assessments of Ted Bundy, Arthur Bishop, and other serial killers, he devised a theory about their ability to compartmentalize that helped to explain the psychological dynamics of offenders who were otherwise socially functional.