A motorist was found guilty of drink-driving after his saliva was found on an airbag which went off after his car hit four stationary vehicles.

Joe Spencer, 22, had left the scene of the accident in Hethersett but his saliva was later found on the airbag.

Spencer, of Woodhaven Way, Wymondham, hit the vehicles in Ullswater Drive, Hethersett, at about 6.15am on November 23 last year, Norwich Magistrates' Court heard.

Spencer was not in court yesterday to answer the charges of drink-driving, failing to stop after an accident and failing to report an accident because he had a 'panic attack' and ran off before his case came up.

But District Judge Nick Watson decided to proceed in his absence.

Spencer had pleaded not guilty to the charges at an early hearing, and Luke Brown, defending, said there was not enough evidence to prove he was at the wheel of his Saab 9-3 Sportwagon at the time.

But prosecutor Oliver Haswell said Spencer's DNA – from his saliva – was found on the car's airbag, which went off during the collisions.

Mr Brown said Spencer's saliva had got on to the airbag after he bought the car in October, when he removed the airbag cover to replace it with a new one.

But the judge said that claim was 'quite fanciful'.

He said: 'There is no suggestion that anyone else's saliva was on the airbag.'

Spencer's mother, Allison Campbell, of Upper Cliff Road, Gorleston, brought a Saab airbag to court to show just how easy it was to remove the cover from the device.

Giving evidence for the defence, she said Spencer bought the 2007 Saab at auction for about £2,000, and he had got a good deal because the airbag light was faulty. She said she bought him a new airbag online, but Spencer discovered he could fix the car's existing device, and merely replaced its cover as it looked newer.

The defence claimed this was when Spencer's saliva – later found by crime scene investigators – got on the airbag.

Mr Haswell said it was folly to have bought the airbag to court, as it was activated by an 'explosive device' and could be dangerous.

Spencer was arrested at 7am on the morning of the incident at his girlfriend's address in Petunia Court, Wymondham.

When he was then tested by police, he was found with 63 microgrammes of alcohol in 100 millilitres of breath – almost twice the legal limit of 35 microgrammes.

Spencer has been disqualified from driving until his sentencing next month.