About 10 head of stock escaped from the trailer and ran loose over the road, running into residential properties and orchards. Six beasts had to be shot by police and landowners due to their agitated state and/or injuries.
A member of the public, who tried to pen one of the beasts, was trampled and required surgery for broken bones to his shoulder.
Traffic was disrupted for about two hours while the roaming animals were rounded up and the scene was cleared.
There was no mechanical defect found with either the truck or trailer, it was a fine day and the road conditions were good, yet Sefton lost control.
Constable Ian Sadler gave evidence the cause of the crash was the result of Sefton's inexperience in driving a full cattle truck.
Sefton had either taken the corner too fast or steered around the corner too sharply after failing to take into account the truck's high centre of gravity, he said.
Sefton disputed these findings.
He told the court he had been driving about 65 km/h over the bridge and slowed as he neared the end of the bridge, and immediately took his foot off the accelerator when he noticed the trailer wheels lifting off the road.
He said he had done his best to steer the truck so it did not crash into anyone or nearby houses, but conceded he had limited experience of driving fully laden stock vehicles.
Sefton's lawyer Bill Nabney argued there was no case to answer because there was no expert technical evidence to support the police allegation of any carelessness.
Mrs Cooper disagreed.
She said she agreed with police the only obvious conclusion was that Sefton had taken the corner too fast or too sharply.
But given that Sefton had no previous criminal history, she discharged him without conviction.