A prison officer slashed a man he believed had raped a woman he knew.
Gary Grimes, 39, attacked his victim with a Stanley knife-type blade in a pub in Lennoxtown, East Dunbartonshire, in December 2018.
The victim required surgery for a number of facial wounds leaving him scarred for life.
First offender Grimes worked at HMP Low Moss in Bishopbriggs at the time.
He now faces jail after pleading guilty to assaulting a man to his severe injury, permanent disfigurement and to the danger of his life.
Grimes – who had his bail continued – had originally faced an attempted murder allegation. He will be sentenced later this month.
On Wednesday, the High Court in Glasgow heard how an Old Firm match had been screened on the television at the Commercial Inn pub on December 29, 2018.
Both Grimes and the victim were later in the busy pub.
The victim saw the prison guard there, but did not speak to him.
Grimes left, but returned to the bar around 10.50pm.
CCTV saw him standing alone before asking staff to turn down music. But, seconds later, he pounced on his victim who was at a table nearby.
Prosecutor Graeme Jessop said: “He approached him and, without warning, lunged towards [the victim] and repeatedly slashed him with a Stanley-type knife.”
The footage then showed Grimes being dragged away by customers as others gave first aid to the bleeding victim.
When police turned up, Grimes was outside the bar and told officers: “I have just slashed a guy who raped a woman I know.”
Further checks revealed the female had made claims to a relative, but nothing was ever reported to police.
The victim suffered a number of facial injuries including a 10cm “deep wound” at the jaw.
Mr Jessop stated: “He required surgery and was then referred to plastic surgery.
“I am advised that there will be scarring.”
Grimes’ current status with the prison service is not known.