The family of Caoimhin Cassidy have expressed their anger that his friends have not come forward with information about his death.
The body of the 18-year-old was found inside a red Mazda 6 that had crashed on the Fairview Road in Londonderry during the early hours of June 1.
Enquiries have led police to believe Caoimhin was not alone in the vehicle.
His great-uncle, Charles 'Nucker' Tierney, said Caoimhin's friends had not helped police with their investigation.
"They haven't come forward, they aren't friends," Mr Tierney told the BBC yesterday.
"If they had a conscience, they will come forward.
"We don't want young people to go to prison. We just want to know what happened."
Mr Tierney criticised people for speculating on the identity of those involved on social media. He said they were "disrupting the investigation".
"If people think they know who is involved, just come forward," he urged.
Police initially believed that the stolen car Caoimhin was travelling in had caught fire as a result of the collision.
However, the results from the post-mortem examination showed that Caoimhin was not seriously injured as a result of a crash, and was most likely still alive when the blaze started.
Following Caoimhin's death police received a report of two men running away from the vehicle on the Fairview Road, heading in the direction of Ferndale.
There were also sightings of a man, possibly injured, walking on the Buncrana Road, past the Skeoge Link Road, towards the border a short time later.
There was widespread anti-social behaviour in the Creggan area of Londonderry on Friday following Caoimhin's funeral.
The disorder was sparked by joyriding youths in two cars in front of St Mary's Church.
In the ensuing chaos, a teenage male was discovered by a police patrol lying on grassland and was taken to hospital where he was treated for puncture wounds to his shins, in what police are treating as a paramilitary attack carried out by dissident republicans.
Meanwhile, Detective Inspector Michael Winters renewed the PSNI's appeal for information.
"We've received a report of two males running away from where the vehicle came to a final halt," he revealed.
"We've also been made aware of sightings of a male, possibly injured, walking on the Buncrana Road, past the Skeoge Link Road, towards the border a short time later."