BBC News NI examines the events that followed her disappearance in 1994.
14 August 1994: Fifteen year old Arlene Arkinson goes missing after attending a disco at Bundoran in Donegal.
The Castlederg teenager was last seen in a car driven by Irish native Robert Lesarian Howard.
21 April 2001: South London teenager Hannah Williams goes missing during a shopping trip.
15 March 2002: Williams's badly decomposed body is discovered in an industrial area of Northfleet, Kent, beside the Thames estuary.
23 March 2002: Howard, a convicted sex offender who had known Williams since 1999, is arrested.
October 2003: Howard is found guilty of raping and murdering the 14-year-old before dumping her body. He is sentenced to life imprisonment although the details of his conviction cannot be reported because he faces separate sex charges in Northern Ireland. He is jailed in County Durham, England.
27 June 2005: Howard, then 61, is found not guilty of murdering Arlene Arkinson. The prosecution had accused him of trying to conceal his movements on the night Arlene went missing and getting others to lie for him. The jury did not know that by then he was already serving life for raping and killing Hannah Williams.
20 September 2005: As reporting restrictions are lifted at Belfast Crown Court, it emerges that Howard's criminal record dates back 40 years.
20 September 2011: Howard wins permission to challenge the holding of an inquest into Arlene's death. His legal team claim the move involves an attempt to undermine the not guilty verdict returned against him.
6 February 2013: Senior Coroner John Leckey rules out holding a full inquest into the murder of Arlene Arkinson within the calendar year because of a strain on resources.
24 June 2015: The long-delayed inquest into Arlene's disappearance is again postponed until November 2015.
2 October 2015: Howard dies aged 71. He remains the only suspect in the murder of Arlene Arkinson. Former PSNI detective Alan McQuillan says chances were missed to save the lives of his victims. Despite 92 searches and a long-running missing persons investigation, Arlene's body has never been recovered.
Child killer Robert Howard, who was the only suspect in the murder of Castlederg teenager Arlene Arkinson, has died aged 71.