The circumstances of the attack must be exceptional in order for the court not to make an order for destruction — and this is a steep hill to climb.
The circumstances need to be special or very unusual. One appeal that proved successful was the tradesman who left the owner's gate (to the secure area) open, the dog got out and bit another visitor.
The district council is the prosecuting authority in these cases of dog attacks, while the defendant is the owner of the dog.
Once the prosecution has proved that an attack occurred, and that the defendant is the owner of the dog, it is then up to the defendant to prove that, on the balance of probability, there was a total absence of fault on their part.
There needs to be physical contact between dog and victim resulting from a deliberate and aggressive action by the dog. This does not necessarily require a bite.
Should a dog be "under control" when an attack occurs, no offence is committed, but the benchmark for "control" is high.
Should your dog be on a lead when it attacks, then it will be found not to have been under control. If your dog is in your fenced off back-yard then it can be deemed to have been in control.
The Dog Control Act has brutal consequences — there may well be no second chance. In reality, it usually depends entirely on the tolerance of the victim to not report the incident.