An inquest in Downpatrick has been unable to determine the exact cause of a three-vehicle crash in 2014 that claimed the life of a 20-year-old man.
Jack Murnin from Downpatrick had been driving towards the nearby town of Strangford to meet a friend for lunch on December 22, 2014.
While taking a right-hand bend it is believed he lost control of his Rover MG and collided with two other vehicles.
He died shortly after the crash from chest injuries.
It is the second tragedy for the family after Jack's father died when Jack was six in a road crash 15 years earlier.
Oil suspected of having leaked from a tractor had been found on the road after Jack's crash, but it could not be proven if it was there before the collision.
The findings were delivered by coroner Brian Sherrard in Downpatrick court yesterday.
He heard forensic evidence that it was likely a "multi-cause" crash.
Damp road conditions, a rear tyre in poor condition on Mr Murrin's MG and going round the tight corner at around 50mph (the speed limit) could all have played a part.
He added that the evidence could not prove the oil was there before the crash, but equally he "could not exclude that possibility".
Members of Mr Murrin's family said they strongly believed oil leaking from a tractor was to blame for Jack's death.
Jack's mother Pauline Murnin said she was frustrated by the lack of certainty.
"The coroner said he can't rule out the oil was on the road but he can't say it was either," she said.
"That's not what I wanted to hear. It can't be proved now, after the fact's too late.
"I know there was oil on the road before the accident.
"People had been warning about it on social media before. Everyone knew, my family even knew.
"So that's hard for me knowing Jack could have slid in the oil, people had been sliding in it all week."
At yesterday's inquest, further evidence was provided that two tractors had driven through the area that day.
It is unknown if this occurred before or after the crash.
A red Massey Ferguson tractor had also driven to the scene after the accident that afternoon, but was redirected by police.
In a statement heard in the inquest, a PSNI constable said he noticed oil on the ground afterwards, but had not taken a registration number.
In the following days, police inspections of tractors on two farms in the area took place but no evidence of oil leaks were found.
A week after the crash, at a police cordon set up around the crash site, a similar looking red Massey Ferguson was stopped by the same PSNI constable.
It was found to be leaking oil and was impounded by police. It is unknown if this was the same tractor, or if it was leaking oil on the day of the accident.
Mrs Murnin said that although she was frustrated with some of the findings, she was glad to hear that her son was not speeding.
"His dad was killed by a drunk-driver 15 years ago when Jack was six. That's why he wasn't a boy racer," she said.
"If he wanted to race he did it in motocross riding. That's how he got his kicks.
"He knew not to do it on the roads. I'm glad that came out and I'd like that to be known."