Parents always believed teenagers were murdered: Tests have finally proved that three youths were strangled. Jason Bennetto reports

SHEILA and John Hanson refused to believe their 15-year-old son David died after sniffing lighter fuel. But the police and forensic scientists insisted they had evidence to prove it.

He was one of three teenagers to have perished in fires between November and February in derelict buildings and garden sheds in Sunderland. All of the youths had died of asphyxiation and were victims of a deadly new craze involving fire and drugs the police said.

In March, Chief Inspector Dennis Cleugh, of Sunderland CID, dimissed reports of a serial killer. He said: 'This is not a murder investigation. We have expert medical evidence that there is nothing suspicious about the deaths.'

In August, a spokesman for Northumbria police said the investigation files had been sent to the Crown Prosecution service in the routine fashion and there was no fresh evidence to suggest suspicious circumstances linking the deaths.

But Mr and Mrs Hanson could not believe their quiet son, who had never shown any interest in drugs, could have got involved in glue sniffing. They said he would have been too scared to go alone to the seafront house where his body was discovered.

All three youths - Thomas Kelly, 18, who was found dead last November, and David Hanson and David Grieff, 15, who were killed in February, - died in remarkably similar circumstances. They had all gone to the same school, Monkwearmouth comprehensive in Sunderland, they had died within a half-mile radius and the circumstances were similar in each case - by the side of each body was a can of lighter fuel.

But the forensic reports still said there was nothing suspicious.

Mrs Hanson said in March: 'There is something far more sinister about these deaths. Somebody is walking about out there who is responsible. I will never believe anything else.'

Yesterday she was proved right when the police announced that her son and the two other youths had been murdered. They had all been strangled by what detectives believe is a serial killer.

A fresh murder inquiry started yesterday. A possible fourth victim is also being considered.

The police argued they did nothing wrong and that the severe damage caused by the fire to the victim's bodies and surroundings had hampered the investigation. The nature of the death also made it difficult to distinguish between death by choking on smoke and fumes and strangulation. It was only after the police had fresh scientific and pathological examinations that the truth was discovered. Police believe the cans of lighter fuel may have been planted by the killer to suggest they were tragic accidents.

The families have accepted the explanation and in what may appear a strange reaction talked yesterday of their 'relief' that their sons had been found to have been murdered rather than branded 'drug abuse victims'.

Mrs Hanson said: 'In a way we feel a sense of relief - we are all relieved.

'We have always said that somebody did it to them - that the boys were not by themselves.

'We have had to put up with headlines like 'Sniffer boy's funeral'. We have heard peope saying things like they were glue- sniffing so what do you expect?'

Her husband, John said: 'People perhaps didn't come forward with information when they thought it was a case of glue-sniffing, but now they know it is murder we hope they will take more notice and if they have information that can help the police to give it.'

Tommy Kelly, a former miner, said of his son: 'He never ever got into any bother and was a quiet lad - all three of them were quiet lads.'

(Photographs omitted)