Two car passengers were killed in a head-on crash with an ambulance travelling on the wrong side of the road, an inquest in Cornwall heard on Wednesday.
Recording open verdicts, the coroner said police had been unable to prove that Graham Dudman, 59, who was at the wheel of the West Country Ambulance Service vehicle, had fallen asleep and then collided with a Ford Fiesta on the A3059 near Newquay last May.
The Fiesta, carrying five young men on their way home after a night out, ended up on its roof after the crash, the inquest at Launceston was told.
David Bellringer, 22, from Wadebridge, died at the scene from multiple injuries. A second passenger Alex Greenaway, 21, from Delabole, died from his injuries in hospital three days later.
Fitness to drive
Recording open verdicts, Edward Carlyon, the assistant deputy coroner for east Cornwall, said there was "no evidence" to prove Mr Dudman had fallen asleep at the wheel.
"The police have made strenuous efforts to attribute the cause of the collision to the proposition that the driver was asleep at the wheel.
"But this is obviously something which is incapable of being proved," he said.
He added: "I am now convinced in my mind that the driver of the ambulance couldn't have been asleep at the wheel."
Mr Carlyon said the police had made a "great play" of investigating Mr
Dudman's fitness to drive on the collision night, but had not done so in the case of the Fiesta driver.
Brothers injured
"I would suggest that having investigated one driver the police should have taken steps to investigate the other," he said.
Mr Greenaway's two brothers Scott and James, the Fiesta driver, as well as friend Philip Cooley were all injured in the crash on 24 May .
The ambulance being driven by Mr Dudman from Wadebridge was on its way to Newquay to provide non-urgent cover.
During police interviews, Mr Dudman, 27 years in the ambulance service, could not say why his vehicle was on the wrong side of the road when it crashed.
'A momentary lapse'
The ambulance driver said he prepared himself for the night shift by eating and sleeping beforehand.
He told the police: "Why I was on the wrong side of the road, I do not know.
"It may have been a lack of concentration, a momentary lapse. I have no recollection. I have to go by what you are saying."
In an earlier interview, he said he had been dazzled by the headlights of the oncoming car, which skidded from his right to left, and he braked as hard as he could.
Mr Dudman is due to appear before Bodmin Magistrates Court on 17 February to face an allegation of driving without due care and attention.