Jack Mallon, 47, attacked 20-year-old Jordan MacKay in South Queensferry, leaving the victim’s girlfriend screaming for help.
Mallon was found guilty of murdering Mr MacKay, while his former girlfriend, Charlene Wilson, was convicted of killing the victim on a reduced charge of culpable homicide.
She phoned Mallon, who arrived to carry out the stabbing after a clash outside a pub.
The jury’s decision to convict Mallon of murder was greeted with cries of “yes” from the public benches at the High Court in Edinburgh yesterday.
And after the hearing the family said in a statement: “We can now get some justice for our Jordan, but at the same time we are saddened knowing our country no longer supports capital punishment.
“Jack and Charlene Wilson will never have the same punishment we do. We are the ones with the life sentence having to live the rest of our lives without Jordan.
“The grief and pain this mindless act of violence has caused is indescribable.
“We can never laugh as hard or love as much as we did when our boy was here with us. Jordan was and always will remain ingrained in our hearts forever more.”
Mallon and Wilson had both denied murdering joiner Mr MacKay, of Kirkliston, in the attack in the early hours of July 13 at The Loan, South Queensferry.
Mr MacKay’s girlfriend, Nicole McKay, 21, said she saw Mallon come out of a car and later saw him “with the knife in the air and Jordan holding his neck”.
Mallon had lodged a special defence claiming that he was acting in defence of himself and his co-accused during their trial at the High Court in Edinburgh.
Mr MacKay was taken to Edinburgh Royal Infirmary following the knife assault but died despite the efforts of medical staff after sustaining a wound that was about 11cm long.
After the attack, Mallon said: “I have stabbed somebody. I think I am going down for it.”
Mr MacKay and his girlfriend had been out socialising in the town where Wilson was also drinking.
Mallon later arrived in South Queensferry by car after Wilson contacted him.
Wilson, 37, from Kirkliston, had been at the Stag Head in South Queensferry’s High Street and had shouted at Mr MacKay’s girlfriend who “laughed it off”, the court heard.
Outside the bar, Wilson clashed with others, and one witness said she had made a threat to get Mallon down to carry out a stabbing.
Footage of the incident outside the pub was caught on CCTV and mobile phones and was shown to the jury.
Wilson was asked how she felt about her antics and said: “Disgusted with myself.”
She said: “I was really drunk that night and I can’t really remember anything about it. I would never want anybody to stab anyone.
“I would never, ever want anybody to be killed.”
But prosecutor Iain McSporran said: “If it had not been for you Jordan MacKay would still be alive, wouldn’t he?”
Wilson said: “I made a phone call but not for that to happen. I never got him to come down to do that.”
Mr MacKay’s mother, Elizabeth, told the court that: “When Jordan died, we died.”
She said her son had been planning to get married, and added that her husband said he would happily change places with his boy.
Mr McSporran said the depressing reality of the consumption of alcohol and the ease with which people carried knives had led to another death.
The judge, Johanna Johnston QC, told Wilson and Mallon: “Each of you has been convicted of criminal responsibility for the death of Jordan MacKay.”
She told Mallon there was only one sentence that could be imposed in his case for murder – life imprisonment.
But the judge will need to set a minimum term he must in jail before he becomes eligible to seek release.
Wilson could also face a life sentence for culpable homicide.
The judge deferred sentence on the pair, who were remanded in custody, until next month.
Detective Inspector Raymond Brown said after the verdict: “This was a senseless attack on a young man who had everything to live for, and serves as a warning of the dangers of alcohol-fuelled violence and knife crime.
“I hope that Jordan MacKay’s family can find some comfort in the guilty verdict.”