Violent Stephen McFarlane carried out the brutal attack within a flat in a row over a bag of cannabis, the brave woman told a jury.

Stephen McFarlane, 25, used a red-coloured circular saw on her boyfriend before cutting his own finger and abandoning that attack — then dragging the man into a bathroom and taking a knife to his left ear, it was stated in evidence.

The woman — who claimed she had then been warned not to ‘grass’ — took prosecutors and defence lawyers by surprise as she delivered her ‘clear and detailed’ testimony from the witness box at Greenock Sheriff Court.

She declared that she is now plagued by nightmares about the shocking incident, which she says will remain with her ‘for the rest of her days’.

The woman told how she was preparing for a ‘quiet night’ in her own home and was in her pyjamas when she received a phone call from Mark McFarlane, 26, for her to come to a flat in the town’s Antigua Street to collect her ‘drunk’ boyfriend.

But once at the property she and her partner were accused of stealing an ounce of herbal cannabis — before McFarlane made a phone call to his brother Stephen, she claimed.

A reduced jury of nine women and four men heard that claims from the woman that she was ordered to strip while the circular saw was taken from a cupboard and then plugged into a wall socket as her boyfriend lay on a bed.

The woman said that she began ‘screaming hysterically’ as Stephen McFarlane used the saw to cut to the bone of the man’s left wrist before returning to the cupboard, grabbing two knives, and ‘chopping’ at his head and body.

She said McFarlane then dragged the man into the bathroom and began to slice his left ear whilst holding him up against a wall.

The alleged assault only came to an end because a man arrived and ordered Stephen McFarlane to stop, the court was told.

In summarising the woman’s evidence, procurator fiscal depute Pamela Brady said: “It sounded like something out of the Kray twins era.” After getting her boyfriend out of the flat, the woman told how Stephen McFarlane came outside — still with both knives in his hands — and warned: “You better not grass.” She told the court that there is a saying in Greenock that ‘grasses get slashes’ but she bravely told police that her boyfriend had been attacked in the flat — after initially saying that she had found him in the street.

Her evidence about the circular saw and baseball bat came out during the week-long trial.

The woman managed to get her blood-soaked boyfriend to a phone box in Lynedoch Street and she called for an ambulance before paramedics found him with a ‘partially detached ear’, the court heard.

A casualty surgeon confirmed that a crescent-shaped cut around his ear could be consistent with the woman’s account that someone had attempted to hack it off.

Prosecutor Mrs Brady said: “There was also a particularly deep cut to the man’s left wrist to the extent that the bone was visible.” Police later found bloodstaining within the Antigua Street flat, bloodstained bedding in a washing machine and the injured man’s blood on Stephen McFarlane’s clothing.

His brother Mark was acquitted of all charges during the trial after the court was told that there was no blood or DNA evidence linking him to the incident.

Forensic scientist Lousie Myers told the court that the chances of blood found on one of the knives not being that of the victim were 370,000 to one.

A fabric arm cast, which had been worn by Stephen McFarlane, had larger amounts of wet blood transferred on to it with the chances of it not being that of the victim put at one-billion-to-one.

The man who was attacked claimed to have ‘no recollection’ of the incident but fiscal depute Mrs Brady pointed out that ‘one very brave young lady’ remembered what had happened.

The prosecutor said: “The woman’s account was clear and detailed and she would not be shaken on it.” The jury found Stephen McFarlane guilty of holding the victim’s hand to a circular saw and repeatedly striking him on the head and body with knives or similar instruments all to his severe injury and permanent disfigurement.

The attack took place within a flat at Antigua Street on 2 August last year.

McFarlane was in breach of a bail curfew ordering him to remain within his Ann Street home between 7pm to 7am at the time of the incident.

He was also found guilty of shouting, swearing, gesticulating, uttering threats of violence and challenging two men and a woman to fight in Greenock’s Lyle Street on 20 June last year.

Co-accused Jordan Moore, 24, of Inverkip Street, Greenock, was found guilty of having baseball bat as an offensive weapon in Lyle Street during that incident.

Sheriff Derek Hamilton deferred sentence on both men until 9 December and remanded them in custody.