A man accused of a biting part of another man's ear off had to be physically restrained after he started throwing items around the dock during his trial.
David Craig Burnie threw water cups and headphones at the perspex screens at Caernarfon Crown Court while hurling abuse at the prosecution.
Earlier the 32-year-old, of no fixed address but formerly of Anglesey, had stepped out of the witness box and approached the prosecutor with raised hands.
He was angry because he had asked for documents which had not been provided against an allegation of wounding with intent.
The jury had heard Burnie and another man, Elfed Richard Jones, had gone to Mr McGough's flat to "get their heads down" after a nights drinking in Bangor.
They arrived shortly after 5am and within minutes began violently assaulting him. Jones was said to have repeatedly punched Mr McGough in the head and slashed his cheek with a knife.
Burnie was said to have punched him and bitten his left ear tearing the top part of it off. Forensic officers later recovered the piece of flesh and it was found to have traces of Burnie's saliva on it.
The first outburst occurred while Burnie was being quizzed by prosecuting barrister Simon Rogers.
Burnie, who had been belligerent and aggressive in answering the barristers questions from the start, began hurling abuse at Mr Rogers.
He had been asked to explain why his DNA on the piece of Mr McGough's ear. When Mr Rogers suggested he was claiming it had been planted Burnie said he found that insulting and became increasingly argumentative.
Asked by the barrister if this was the way he had behaved in Mr McGough's flat Burnie stepped out of the witness box and started making his way towards Mr Rogers. He stood his ground and Burnie was restrained by two dock officers.
"I'm f****** angry, I'm f****** fuming," Burnie shouted.
The hearing was adjourned for several minutes before it was able to resume although Burnie remained argumentative during the remainder of the cross-examination.
Later, as Mr Rogers gave his closing speech to the jury, Burnie interrupted three times telling the barrister at one stage to "stop bull*******g". He was repeatedly warned about his behaviour by Judge Rhys Rowlands.
But despite the warnings Burnie again interrupted Mr Rogers slow handclapping him from the dock.
Adjourning the hearing the judge ordered Burnie to be taken to the cells.
He was told by dock officers to calm down but refused to do so and was handcuffed before being led away.
The judge told the jury to make allowances for Burnie's "erratic behaviour" suggesting he was under a great deal of stress.
The jury took an hour to unanimously convict him of the charge. He was not in court to hear the verdict. Defence counsel Brian Treadwell said he wished to be present and would try to be calm if an adverse verdict was delivered. The judge said he could not allow him to be present.
Adjourning sentence the judge said both men would be sentenced together and an assessment of the risk Burnie poses to the general public was required.
There was no application for bail and Burnie was remanded in custody.
After the hearing investigating officer DC Saran Henderson said: "We welcome the conviction handed down today at Caernarfon Crown Court.
‘This was an unprovoked attack on a defenceless victim by two thugs, resulting in Burnie biting off part of the victim’s ear – a truly disgusting barbaric act, for which Burnie has shown no remorse."
