Police remain committed to pursuing all viable lines of inquiry on the Stephen Lawrence case, officers said on Monday.
The investigation will be featured on the BBC's Crimewatch programme tonight, a week after the 20th anniversary of the racist attack.
Detective Chief Inspector Clive Driscoll will take viewers back to the scene in Eltham, south-east London, and run them through the events of that night in an appeal to a number of witnesses who it is believed have never come forward.
The programme also features an interview with Stephen's mother, Doreen Lawrence, who talks about why it remains so important for any outstanding witnesses to come forward.
A Scotland Yard spokesman said: "Despite securing two convictions in this case, the investigation remains open and officers believe there were individuals in the vicinity of the murder who have never come forward."
These include two men who got off a bus at the stop opposite where Stephen was attacked and walked southbound along the east side of Well Hall Road, a man who ran from the area of Well Hall Road roundabout to the bus stop on the same side of Well Hall Road as the attack, a man who was walking on the east side of Well Hall south of the roundabout, opposite the Coronet cinema, wearing a distinctive green jacket with a large 'V', and anyone else in the general vicinity, such as those outside the cinema and on passing buses.
On the evening of April 22 1993, aspiring architect Stephen was stabbed to death by a group of up to six white youths in an unprovoked racist attack as he waited at a bus stop in Well Hall Road with a friend.
After an initial confrontation he was stabbed in nearby Dickson Road. He was able to escape from the group and managed to run a distance of around 130 yards before collapsing. The suspects ran off down Dickson Road.
In January 2012 Gary Dobson and David Norris were found guilty of being involved in the attack and sentenced to life imprisonment, after a forensic review of the case found significant new scientific evidence on clothing seized from their homes following the murder.
DCI Driscoll said: "Although two individuals are serving a life sentence in connection with this murder, we have always known there were other people involved in the attack. As such this investigation remains open and my team is committed to pursuing all viable lines of inquiry available to us. It is hoped this appeal will assist with our inquiries.
"We believe there were people in the area that night who may have seen something. Not the murder itself necessarily, but events or individuals leading up to the event. I am taking this opportunity to appeal directly to those people to come forward and speak to us. You may think you won't remember something from so long ago, but we would still implore you to come forward."
:: Anyone with information was asked to contact the incident room on 020 8785 8310 or Crimestoppers anonymously on 0800 555111.