Alcohol-fuelled Stephen Thompson, described as a 'gentle giant', carried out a frenzied knife attack on a young couple following a dispute at a party at his house in Boldon Colliery in the early hours of January 14.
When the 27-year-old, who suffers from learning difficulties, asked all of the guests to leave his property he got into an argument with the female victim - who's partner then intervened and punched Thompson a number of times in the face, causing him to fall onto the floor.
Thompson then produced a craft knife and slashed the male victim, slicing his forearm and neck.
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Newcastle Crown court heard how the couple then left the house, but were followed by Thompson - who was still waving the knife in a slashing motion towards the man.
However he accidentally slashed the female across the face, causing blood to "go squirting" everywhere.
The court was told that the defendant then attempted to ditch his bloodied t-shirt in a nearby garden.
Prosecutor Emma Dowling said: "The situation was chaotic.
"There was an injury to the female's left shoulder and a very serious injury to the left side of her face. A long linear wound is the best way to describe it.
"The wound was deep and has left a lasting physical scar that she knows she will have to live with for the rest of her life.
"At first she thought she was being punched. Then she heard Thompson say 'I am so sorry I did not mean to do that'.
"She was drifting in and out of consciousness.
"Now she is learning to cope with her life changing injuries."
The court was told how the female victim suffered a 10-11 cm laceration from her left cheek to her chin, and needed to have over 33 stitches in her face and left shoulder.
In a victim personal statement, the victim described how she refused to look in the mirror for three days after the attack because she was so scared of seeing her injuries.
The court heard how she still has nightmares about the attack and it will take her time to accept her injuries.
The male victim said he has been left "frightened" by the attack and suffered superficial lacerations to the face and forearm.
Thompson, of Charles Street, Boldon Colliery, admitted charges of wounding, wounding with intent, possession of a bladed article and possession of cannabis.
John Wilkinson, defending, explained that the defendant suffered from a number of learning disabilities and a depressive disorder.
He said: "He has the presence of an adult but you will know that he essentially his intelligence levels and comprehensive levels fell somewhere between someone of the age of five years and 11 months to seven years of age.
"He has the behaviour of a child. He can't be relied upon to switch the cooker off. He finds taking the bus on his own challenging.
"Clearly your honour, you are dealing with someone has significant issues.
"He has never been in trouble before and he is someone who is of good character.
"He does not realise that he caused these injuries. As soon as he knew the injury was caused to the female victim he said he was sorry but by then it was too late as the damage was done.
"He is devastated.
"I must ask your honour in this case to temper justice with mercy."
Mr Wilkinson read out a number of character references which described the defendant as a "gentle giant" who was "kind and quiet and always kept himself to himself."
However Judge Sarah Mallet imposed a five-and-a-half year custodial sentence.
She told Thompson: "You were aggressive and threatening. You waved the Stanley knife in a slashing motion but you slashed the female complaint.
"She has a lasting scar to the face that she will always have. The problems are carrying on. The injuries in my view are very serious.
"The problem on this day began when you asked people to leave. I accept that you had the Stanley knife because you were having a carpet fitted earlier that day.
"I take into account that your age and intelligence levels don't tally.
"I accept that you are sorry and I accept that that is genuine."
Thompson was also given a life-long restraining order against the female victim.