Question: Child 44 is loosely based on the case of the killer who confessed to how many murders?

Context articles: Matti Haapoja
Andrei Chikatilo
Albert Fish
VVT (gang)
Child 44
Frank Schweihs
Child 44 (film)
The Twa Magicians
Frank Abbandando
Worldview Entertainment

Matti Haapoja (September 16, 1845, Isokyrö – January 8, 1895, Turku) was a Finnish serial killer who was much covered by the press at the time of the murders.
 The exact number of his victims is unknown.
 He was convicted of two murders and was scheduled for a trial for his third murder trial when he committed suicide in his cell.
 He can be linked to seven other identified murder cases, but most of those happened during his exile in Siberia and are poorly documented, so his involvement is not certain.
 It is claimed that he confessed to 18 murders, but there are no details about this supposed confession, and the figure should be regarded as unreliable.
 Some sources estimate his total number of murders as 22–25.
 He also non-fatally wounded at least six men in knife fights.
Andrei Romanovich Chikatilo (Russian: Андрей Романович Чикатило , Ukrainian: Андрій Романович Чикатило ; 16 October 1936 – 14 February 1994) was a Soviet serial killer, nicknamed the Butcher of Rostov, the Red Ripper, and the Rostov Ripper, who committed the sexual assault, murder, and mutilation of at least 52 women and children between 1978 and 1990 in the Russian SFSR, the Ukrainian SSR and the Uzbek SSR.
 Chikatilo confessed to a total of 56 murders and was tried for 53 of these killings in April 1992.
 He was convicted and sentenced to death for 52 of these murders in October 1992 and subsequently executed in February 1994.
Hamilton Howard "Albert" Fish (May 19, 1870 – January 16, 1936) was an American serial killer.
 He was also known as the Gray Man, the Werewolf of Wysteria, the Brooklyn Vampire, the Moon Maniac, and The Boogey Man.
 A child rapist and cannibal, he boasted that he "had children in every state", and at one time stated the number was about 100.
 However, it is not known whether he was referring to rapes or cannibalization, nor is it known if the statement was truthful.
 He was a suspect in at least five murders during his lifetime.
 Fish confessed to three murders that police were able to trace to a known homicide, and he confessed to stabbing at least two other people.
 He was put on trial for the kidnapping and murder of Grace Budd, and was convicted and executed by electric chair.
 His crimes were dramatised in the 2007 film "The Gray Man", starring Patrick Bauchau as Fish.
VVT is a Tamil gang in Toronto believed to be named after the Sri Lankan town of Valvettithurai.
 It was founded in the early 1990s by Tamil immigrants.
 The VVT had a strong presence in the west end of Toronto (in particular in Etobicoke and certain areas in Old Toronto and East York) and was regarded as being very business savvy and motivated by the profits of crime.
 The VVT were considered to be highly organized with members ranging in age from their early teenage years to men in their 30s, with members from to 100-500 strong.
 In the mid to late 1990s and early 2000s the VVT had an ongoing war with another powerful Tamil gang called the AK Kannan based out of Scarborough.
 There was a brief truce in 1998 after community members brokered a peace deal in a Richmond Hill Hindu temple; however, a murder a year later renewed the fighting.
 VVT is behind many murders in the 1990s.
Child 44 (published in 2008) is a thriller novel by British writer Tom Rob Smith.
 This is the first novel in a trilogy featuring former MGB Agent Leo Demidov, who investigates a series of gruesome child murders in Joseph Stalin's Soviet Union.
Francis John Schweihs (February 7, 1932 – July 23, 2008), aka "Frank the German", was an American gangster, who worked for The Outfit, the organized crime family of Chicago.
 At the time of his death, federal prosecutors planned to indict him for numerous crimes, including murder.
 It is believed he had participated in, or had knowledge of, many murders going back decades, including brothers Anthony "Tony the Ant" Spilotro and Michael Spilotro, Allen Dorfman of the Teamsters Union, a disgraced Chicago cop, Outfit associate and informant Dick Cain, Outfit boss Salvatore "Sam," "Mooney" Giancana, loanshark Sam "Mad Sam" DeStefano, Outfit hitman Charles "Chuckie" Nicoletti and others.
Child 44 is a 2015 mystery thriller film directed by Daniel Espinosa, written by Richard Price, and based on Tom Rob Smith's 2008 novel of the same name.
 The film stars an ensemble cast featuring Tom Hardy, Gary Oldman, Noomi Rapace, Joel Kinnaman, Paddy Considine, Jason Clarke, and Vincent Cassel.
 It was released on 17 April 2015.
 Both the novel and the film are very loosely based on the case of Soviet serial killer Andrei Chikatilo, who had been portrayed in the earlier film "Citizen X".
"The Twa Magicians", "The Two Magicians", "The Lady and the Blacksmith", or "The Coal Black Smith" (Roud 1350, Child 44) is a British folk song.
 It first appears in print in 1828 in two sources, Peter Buchan's "Ancient Ballads and Songs of the North of Scotland" and John Wilson's "Noctes Ambrosianae" #40.
 It was later published as number 44 of Francis James Child's "English and Scottish Popular Ballads".
 During the 20th century, versions of it have been recorded by a number of folk and popular musicians.
Frank Abbandando (July 11, 1910 – February 19, 1942), nicknamed "The Dasher", was a New York City contract killer who committed many murders as part of the infamous Murder, Inc. gang.
Worldview Entertainment is an American independent motion picture company that finances and produces theatrical quality feature films for worldwide distribution.
 The company was founded in 2007 and is based in New York City.
 Worldview has produced films including "Child 44", "Birdman", "Blood Ties", "The Green Inferno", and "Killer Joe".