Child 44 is loosely based on the case of the killer who confessed to how many murders?
Child 44 (film):  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". Andrei Chikatilo:  Chikatilo confessed to a total of 56 murders and was tried for 53 of these killings in April 1992.
56