Dad-of-three James Aird deliberately turned up at the lad’s house at a time when he thought the boy’s family were out. The 33-year-old Mountblow man then pounced on his teenage victim as he put his nephew’s pram outside the front door.

He pulled him into the common close where he subjected him to a vicious and prolonged attack which left the youngster hospitalised.

The savage assault was described as a “callous, cold and cowardly attack by a grown man who should have known better”.

It only ended after the blood-soaked teen — who has now been left permanently disfigured — escaped into a neighbour’s home.

Unemployed Aird — who was on bail at the time he carried out the stabbing — has a lengthy criminal history spanning six pages including previous convictions for carrying weapons. He had argued that he had been acting in self-defence.

However, last week found a jury found him guilty of the attack and he was given a lengthy jail sentence.

Dumbarton Sheriff Court heard an angry Aird had turned up at the 13-year-old’s door armed with weapon and looking for a fight on the morning of April 16 and that he had thought his victim would be by himself.

He then tried to strike the youngster with something sharp, which witnesses describe as a knife or a corkscrew, before throwing him to the ground, pulling him from the house and kicking him in the head.

Aird then chased the lad down a flight of stairs where he pinned him in a corner and repeatedly stabbed him.

Prosecutor Sarah Healing said: “James Aird went to the locus looking for trouble. Trouble is exactly what he found. Trouble is exactly what he caused.

“In a civilised society there’s absolutely no place for a man who’s 32 years old to viciously assault a 13-year-old child.” A horrified teen witness to the brutal attack said he was first alerted to the fact that something was wrong after he heard cries for help coming from outside his home.

But as he opened his front door he said he was met by a frightening sight, adding: “I could see a boy getting stabbed.” The onlooker recognised the attacker as Aird and said that he watched on as he stood above his young victim, holding him down in a corner — stabbing him more than five times with a knife or similar looking weapon.

He claimed he then attempted to stop the knifing by shouting at Aird using his nick-name “Junior” but to no avail.

The victim eventually managed to shove his attacker out the way and run into the witness’ home.

The pair then locked the door behind them and phoned the police.

Detectives who had been alerted to the incident found Aird about 40 minutes later walking along the road in Duntocher.

They detained him after being told he had been identified as a suspect for the assault and took him to Clydebank Police Office where he declined the opportunity to speak to a solicitor prior to being interviewed.

Aird then denied knowing anything about the assault and said he had no reason to be at the scene.

But his attitude changed after officers mentioned his victim’s name and he soon requested a lawyer.

After a telephone conversation with a solicitor he then replied “no comment” to the majority of the questions put to him.

But in evidence Aird changed his story and said that he had gone up to his victim’s home in order to speak to the youngster’s sister about something.

He told jurors that after arriving at the scene he was immediately confronted by the teen and attacked.

He said: “He threw a punch at me which struck me in the nose and the top lip. At that stage I was quite shocked and surprised — I wasn’t expecting to get punched.” Aird went on to say that a struggle ensued and the pair fell down some stairs before he was able to leave.

He also admitted that he had lied to the police during his interview and said: “I just buried my head in the sand.

“Who’s going to believe an adult over a child?” On Wednesday a jury of eight women and seven men took less than an hour to reach a guilty verdict and Sheriff Simon Fraser Jailed Aird, of Brunswick House, Mountblow, for three years and six months.

He said: “I don’t know what lay behind this, I have my suspicions, but really what lay behind it doesn’t matter. The fact of the matter is you went round to attack a 13-year-old.

“You attacked that 13-year-old, you dragged him out of his house, you kicked him, pursued him down stairs and struck him on the head and body with a knife or similar instrument to his injury and permanent disfigurement.

“I have to say that my first thought was that I might have to remit you to the High Court of Justiciary for sentence but I take account of the fact you have no previous convictions for violence, although you have previous convictions for virtually everything else.”