The massive beast – which weighed more than six stones – bit a neighbour’s eight-year-old daughter on the face.
Witnesses told a jury trial at Livingston Sheriff Court that a large flap of the youngster’s cheek was ripped off and she was bleeding profusely as a result of the attack.
She needed 40 stitches to close the gaping wound and has been left scarred for life. Doctors say she will also suffer a loss of sensation on her face as a result of the severe injury.
Corcoran, 63, said he had blocked the gate of his son’s garden with a chair to stop the dog escaping when he attended a summer barbecue there in July 2013.
He sat in front of the gate in the belief that the dog would not be able to get out because the garden was surrounded by a four foot high fence.
But when little Heather Halliday passed by on her scooter and shouted over to ask if anyone had seen her sisters, the Rottweiler leaped over the fence towards her without warning.
It landed on the youngster and savaged her face before guests dragged it off and put it on a lead. Police were called and the animal was destroyed the following day.
Corcoran, grandfather from Castlebrae Grove, Edinburgh, said the dog had been playing with other children in the garden before the shock attack.
He denied allegations that he had had to order the animal down from the fence when it barked at other children earlier. He also denied claims by his son Kevin and daughter-in-law Kat that they had said the dog should be put on a lead minutes before the incident.
Asked if he’d have accepted ownership of the dog from Kevin if he knew it was dangerous, Corcoran replied: “Definitely not.”
He added: “I felt really dreadfully bad for the injuries caused to the wee lassie. I don’t feel very happy about it at all.”
The jury took two hours to return a majority verdict finding the charge against Corcoran not proven and he was acquitted. Outside court he spoke of his relief at the verdict, adding: “It was the right decision.”
The girl’s parents were not available for comment.