Nikki Allan murder: Crimewatch appeal over 1992 killing
The unsolved murder of a seven-year-old girl found beaten and stabbed in a derelict building will be the focus of a Crimewatch appeal later.
Sunderland schoolgirl Nikki Allan was killed in October 1992 and despite a number of arrests, no one has been convicted of her death.
Northumbria Police hope the programme will "jog someone's memory".
A neighbour was acquitted of murder following a trial two years after Nikki's murder.
George Heron had confessed to the killing but a judge ruled police had used "oppressive methods" during questioning and he was found not guilty.
He was later ordered by a civil court to pay Nikki's family damages.
Nikki was found on 7 October in the Old Exchange Building near her home at Wear Garth.
Det Supt Roger Ford said: "This was an extremely brutal attack on a defenceless seven-year-old girl and 21 years after it happened it's still talked about in Sunderland and the local area.
"Nikki's family have been left devastated by what happened and we will never give up trying to find her killer."
Mr Ford said the "dark and derelict" building was used by "drug takers, vagrants and local youths".
"Lots of people used to come and go from the building and we want anyone who used to spend time there, for whatever reason, to ring us and talk to us about what they remember about the place, especially the names and details of anyone who they know visited or spent time there."
The programme includes a reconstruction and an interview with Nikki's mother.