THE cause of a car crash that left two women dead is likely to remain a mystery, a coroner said yesterday.

Disqualified driver Stephen Dack was jailed for two-and-a-half years last year after he lost control of his van on the A67, between Gainford and Piercebridge, near Darlington.

Dack, 44, who is profoundly deaf and also without speech, struck farmer's wife Irene Stephenson, who was picking litter yards from her home.

Dack's van then veered into a car on the other side of the road, killing 88-year-old Sarah Thompson, from Darlington, and seriously injuring her daughter, Carol, who was driving the car.

At the time, Dack told police he could not remember what had happened and that he had suffered some kind of blackout or seizure just prior to the accident. He denied that he had fallen asleep at the wheel.

At an inquest in Darlington yesterday, Coroner Andrew Tweddle said that despite a lengthy police investigation the exact reasons for the crash would remain "a matter for conjecture".

Returning a verdict of accidental death, Mr Tweddle said: "All those involved in the matter will draw their own conclusions but, unfortunately, the exact reasons will remain a matter for conjecture."

Medical reports carried out at the time failed to find evidence that Dack was suffering from any condition that could have contributed to a blackout.

John Lowes, who was driving behind Dack's Vauxhall van at the time of the accident in December 2002, said despite clear conditions he saw the van ahead of him drift off the road.

Mr Lowes, of Middleton, in Teesdale, told the inquest: "He seemed to be heading for the pedestrian on the grass verge. At the time, I remember thinking he's going to straighten up in a minute, but he never did."

Mrs Thompson, 57, had been tidying up the grass verge close to her home when she was hit.

Her husband, Peter, said at the time: "She couldn't stand litter. She had gone out to tidy up. She was a hard-working, home-making person.

"Nothing was ever any trouble to her, she got on and did it."

Dack, of Walker, Newcastle, who worked as a labourer for construction company Mowlem, had been disqualified for drink-driving a few months earlier, but failed to tell his employer because he feared losing his job.