 DATE: When John is talking to Frank in the past (1969) he refers to  the murderer as being a "Serial" as in Serial Killer. Frank  immediately understands what a "Serial" is but the term Serial  Killer was not "invented" until the 1970s. The term (serial killer)  is widely believed to have been coined either by FBI agent Robert  Ressler or by Dr. Robert D. Keppel in the 1970s