Cold North Killers: Canadian Serial Murder is a 2012 Canadian non-fiction book written by Lee Mellor and published by Dundurn Press.
 It documents the lives of sixty Canadian serial killers, with the earliest being Edward H. Rulloff and the most recent being Russell Williams.
 The book uses Katherine Ramsland's interpretation of what constitutes a serial killer—someone who has killed at least two people on two separate occasions, and who attempted to or likely would have killed again—as outlined in her 2007 book "The Human Predator".
 "Cold North Killer's" own definition of what constitutes a Canadian serial killer includes both Canadians who committed murder abroad (such as Keith Hunter Jesperson and Gordon Stewart Northcott) and non-Canadians who committed murder in Canada (like William Dean Christenson and Earle Nelson).
Keith Hunter Jesperson (born 6 April 1955) is a Canadian-American serial killer who murdered at least eight women in the United States during the early 1990s.
 He was known as the "Happy Face Killer" because he drew smiley faces on his many letters to the media and prosecutors.
 Many of his victims were sex workers and transients who had no connection to him.
Gary Leon Ridgway (born February 18, 1949) is an American serial killer known as the Green River Killer.
 He was initially convicted of 48 separate murders and is presumed to be responsible for more than 90.
 As part of his plea bargain, an additional conviction was added, bringing the total number of convictions to 49, making him the most prolific American serial killer in history according to confirmed murders.
 He murdered numerous women and girls in Washington State during the 1980s and 1990s.
Bible John is the nickname of a serial killer who is believed to have murdered three young women after meeting them at the Barrowland Ballroom in Glasgow, Scotland, between 1968 and 1969.
 The killer has never been identified although the known movements and modus operandi of convicted Glaswegian serial killer Peter Tobin suggests that he may have been behind the killings.
 However, this has never been proven and the case remains unsolved.
Cold Fish (冷たい熱帯魚 , Tsumetai Nettaigyo ) is a 2010 Japanese horror-drama serial killer film directed by Sion Sono.
 The film is about a quiet and unambitious owner of a tropical fish shop whose life and family are taken over by a fellow fish entrepreneur who happens to be a serial killer.
 The film is loosely based on the exploits of two Tokyo serial killers, Sekine Gen and Hiroko Kazama, a husband and wife duo who owned a pet shop and murdered at least four people.
Phil Stanford is an American journalist and author based in Oregon.
 Stanford is best known for his work on the murder of Oregon Department of Corrections director Michael Francke and his efforts to prove the innocence of Frank Gable, the man who was convicted of the crime.
 His 1994 "Oregonian" series on the “Happy Face Killer” case resulted in two innocent people being released from prison.
The Smiley face murder theory (variations include Smiley face murders, Smiley face killings, Smiley face gang, and others) is a theory advanced by two retired New York City detectives, Kevin Gannon and Anthony Duarte, that a number of young men found dead in bodies of water across several Midwestern American states over the last decade did not accidentally drown, as concluded by law enforcement agencies, but were victims of a serial killer or killers.
 The term "smiley face" became connected to the alleged murders when it was made public that the police had discovered graffiti depicting a smiley face near locations where they think the killer dumped the bodies in at least a dozen of the cases.
 The response of law enforcement investigators and other experts to Gannon and Duarte's theory has been largely skeptical.
Juan Díaz de Garayo y Ruiz de Argandoña, also known as "The Sacamantecas" ("The fat extractor" in Spanish) (October 17, 1821 – May 11, 1881), was a Spanish serial killer active near Vitoria, Álava, who strangled five women and a 13-year-old girl, and attacked four other women during two different periods, 1870 to 1874 and 1878 to 1879.
 A lust-motivated serial killer, Garayo first killed prostitutes after hiring and sleeping with them consensually, but grew more disorganized and violent as time went on, attacking, raping and murdering women that he saw walking alone in the country.
 His last two victims, murdered in consecutive days, were also stabbed, and the second was disembowelled.
The Colonial Parkway Killer was an apparent serial killer believed to have murdered at least eight people along the Colonial Parkway of the U.S. Commonwealth of Virginia (or nearby) between 1986 and 1989.
 During that time, three couples were murdered and one couple is missing and presumed to be dead.
 The killer has never been identified, and his or her whereabouts remain unknown.
Happy Face Killer is a 2014 Canadian-American television film inspired by real-life events of the hunt and capture of serial killer Keith Hunter Jesperson.
 The film premiered on March 1, 2014, on the Lifetime network and starred David Arquette as Jesperson.
 Gloria Reuben played Melinda Gand, the lead FBI case investigator.

Question: Happy Face Killer is a film based on a serial killer who murdered at least how many women?
Answer: eight