The 13-year-old girl was battered to death by an iron tent peg on February 15, 1997, as she painted a patio door in the garden of her Hastings home.
Two decades later her killer remains unknown – Billie-Jo’s foster father Sion was cleared of murdering the Helenswood schoolgirl after spending six years in jail.
A post on the website, Justice for Sion Jenkins, called for police to reopen the case and ‘show the moral courage to own its past’.
“The story of Billie-Jo Jenkins cannot have a happy ending, but it should have a truthful one,” the post says.
“There are individuals with vested interests who may hope that after twenty years no-one will still be asking, ‘who killed Billie-Jo?’
“There are still many people in all parts of the country whose concern has never wavered.
“For that reason the insistent voice of reason still asks that question. Someone knows the answer and it’s time to tell the truth.”
Mr Jenkins was arrested nine days after the schoolgirl’s death and was found guilty at Lewes Crown Court on July 2, 1998. He was freed on appeal pending a retrial in 2004.
The jury in two subsequent retrials failed to reach a verdict and Mr Jenkins was formally acquitted in 2006.
In August, 2010, Mr Jenkins lost his bid for compensation over the six years he spent in prison.
The Observer contacted Sussex Police to ask if a renewed appeal for information would be issued to mark the anniversary of Billie-Jo’s killing.
A police spokesman replied: “Yes as previously stated, this case is unresolved, and any new information that might lead to new lines of enquiry would be assessed, and investigated wherever necessary.
“However there has been no new information since the end of the second trial ten years ago and there is no current work on the case.
“There has been no further review of the case since the second trial and we have no plans for any activity to mark the 20th anniversary.”
In January, 2008, a memorial bench for the teenager was unveiled in Alexandra Park.
Billie-Jo’s friends raised money for the bench which was designed by local artist Joc O’Hare.
The ‘child-friendly’ bench was made from locally felled English oak and engraved with a message to Billie-Jo from her friends.
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