Police officers followed a trail of blood from wounded Robbie Morrison to the home of his attacker in Edinburgh’s Wester Hailes area.
The ex-Scottish infantryman was knifed in the leg by Kristian Nelson during an assault and later died in hospital.
A judge told Nelson at the High Court in Edinburgh that he had had the chance to throw the knife away but deliberately used it to stab his victim.
Lord Glennie said: “You have an unenviable record, including two offences of assault to injury or severe injury and one assault with a hammer. This time it was a knife and the consequences were fatal.”
The judge told Nelson that he would have jailed him for 10 years, but for his earlier guilty plea to culpable homicide.
Nelson, who was originally accused of murdering Mr Morrison, previously admitted a reduced charge of killing his victim
He admitted striking him on the leg with a knife at Dumbryden Gardens, in Edinburgh, on August 22 last year.
Unemployed Nelson, 37, formerly of Dumbryden Gardens, admitted stabbing the victim, but said: “I didn’t mean to kill him.”, the court heard.
Nelson’s co-accused Colin Craig, 46, of Murrayburn Place, in Edinburgh, had also originally faced a charge of murdering Mr Morrison, 31, but the Crown earlier accepted his guilty plea to assault.
Craig tripped Mr Morrison, who fell to the ground, after he tried to run away following a confrontation with Nelson. He also dumped the knife used to kill the victim along with a bloodstained jumper in a canal.The judge deferred sentence on Craig for a year.
Advocate depute Steven Borthwick told the court that Mr Morrison, an only child who had a young daughter, left the Army in 2011 after six years service.
He said that following his military service he became involved in substance misuse and it was believed be bought drugs in the Wester Hailes area, but at the time of his death was seeking help with his problem.
The prosecutor said: “The extent to which the accused and the now deceased knew one another is not entirely clear. The motive for the attack which led to the death of Robbie Morrison is not known.”
He added: “There is some information to suggest that the now deceased owed a debt to a third party and the at the confrontation between Robbie Morrison and the accused arose as a result of that debt.”
Mr Borthwick said the Crown was unable to give a reliable and undisputed version of events.
But he added: “What is clear and accepted is that Craig tripped Mr Morrison, causing him to fall to the ground. Shortly thereafter Nelson used a knife to stab him to the rear of his left thigh.”
The 15 centimetre long wound which went through the thigh damaged a major blood vessel.
The stabbing victim got away from the scene of the attack. A woman noticed a blood trail on a path he used and followed it and found him sitting on the ground with his back to a fence.
Mr Borthwick said: “His leg was covered in blood and when he moved the leg, blood was splashing from it.”
Paramedics and police arrived and Mr Morrison told them he had taken drugs that day and described the knife used on him as “big”.
The prosecutor said: “Police officers followed the blood trail which led them to an area outside 77 Dumbryden Gardens. There was an unbroken trail of blood from where Robbie Morrison had been found to the public pathway outside the rear of Dumbryden Gardens.”
Nelson emerged from the address and told an officer that he had heard two males shouting outside his house and saw one running off, pursued by the other.
The court heard that Craig later said that Mr Morrison had tried to run away and that Nelson told him to stop him so he tripped him
He said they began fighting and Nelson produced a knife and stabbed Mr Morrison on the leg, said the advocate depute.
Mr Morrison stopped breathing on the way to hospital and was given resuscitation treatment. He underwent surgery but his condition deteriorated and he died in the early hours of August 25.
His DNA was found in blood discovered on jeans and a training shoe taken from Nelson.
Solicitor advocate John Scott QC, for Nelson, said that he was on the heroin substitute methadone at the time of the offence.
He said Nelson had shown “genuine remorse” for the offence.