His parents divorced when he was nine and he and his siblings (two brothers and a sister) were placed in foster care and underwent psychiatric treatment for six years at the Maudsley Hospital in Camberwell.
[10] At age 13, Napper underwent a personality change after a family friend sexually assaulted him on a camping holiday.
[9] In October 1989,[11] police had rejected information conveyed in a phone call from Napper's mother that her son had admitted to committing a rape on Plumstead Common.
However, it emerged at the time of Napper's second conviction, that the rape of a 30-year-old woman, in front of her children, eight weeks earlier, had been reported to have occurred in a house which backed onto Plumstead Common.
The crime scene was reportedly so grisly that the police photographer assigned to the case was forced to take two years' leave after witnessing it.
[12] Napper is also believed to have committed most or all of the attacks attributed to the "Green Chain Rapist" (named after the Green Chain Walk – a string of leafy pathways linking large parts of southeast London) who carried out at least 70 savage attacks across south-east London over a four-year period ending in 1994.
[10] During the investigation into the rapes, Napper had been eliminated due to his 6' 2" height, as detectives had decided to exclude anyone over 6' based on the description of a 5' 7" rapist.
[16][17] The investigation to find Nickell's murderer resulted in the attempted prosecution of an innocent man, Colin Stagg, until, in 2004, advances in DNA profiling revealed Napper's connection to the case.