Damian Rzeszowski, 31, has today been found guilty of the manslaughter of six people including his own wife and children by a court in St Helier, Jersey.
He was cleared of their murders on the grounds of diminished responsibility.
The brutal deaths leading to the trial was one of the worst crimes Jersey has ever experienced.
Damian Rzeszowski killed his wife, his two children, his father-in-law, his wife's best friend and her young daughter during a frenzied knife attack.
The attacks are thought to have been the result of a jealous rage after he learnt his wife had been having an affair.
The horrific events unfolded at the Rzeszowski's rented flat in the centre of St Helier on an otherwise peaceful Sunday afternoon in August 2011.
The family and their friends had been relaxing after a barbecue when the bloodshed began.
Detectives believe that he first killed his father-in-law, 56-year-old Marek Gartska, as he sat in his bedroom.Then the builder went into the kitchen and began to slaughter his own children.
First was his two-year-old son Kacper, who was sitting at the dining room table. The little boy was stabbed five times in the chest with one knife and then eight times in the back with a second knife.
Rzeszowski then turned the knives on his five-year-old daughter Kinga, who was stabbed 16 times.
After her it was her playmate, five-year-old Julia de la Haye. She was attacked in two different locations and also had a total of 16 stab wounds.
He then chased the two surviving women through the building. He caught up with Marta de la Haye and stabbed her multiple times.
She had just enough strength to escape through the front door but then collapsed in the street and died.
His terrified wife, Izabela, first escaped through the back windows onto the small courtyard patio, but with no escape she ran back through the flat and out in the street.
Neighbours realised she was being followed and tried to intervene but could not prevent Rzeszowski attacking her with both knifes. She was taken to hospital but later died of her injuries.
Rzeszowski then used the knife to stab himself in the chest twice as other residents in the normally peaceful crescent of Victorian houses looked on. Although he had a punctured lung, he survived.
Ms Rzeszowski, who was 30, had admitted to him that she had been having an affair. It had caused a rift and Damian had tried to take an overdose a month before the killings.
However, the family were trying to overcome the difficulties and had gone back to their native Poland for a three-week holiday. It was shortly after their return that the attacks took place.
His colleagues from the building company where he worked gave evidence to the court. They described a hard-working, skilled craftsmen but said he had changed in the last few months.
They said that he "looked like he was going to blow".
The court also heard that he had shown flashes of a violent temper, although not towards his wife or children. He could not accept that his marriage was over and had been to his GP complaining that he felt suicidal.
Rzeszowski pleaded guilty to manslaughter due to diminished responsibility.
The court heard medical evidence that suggested he had changed his story three times and that he was aware of what he was doing on the afternoon that he killed his victims. Doctors for the defence argued that he had been hearing voices in his head and he was mentally unstable.
Marta de la Haye was Izabela's best friend and had married a local man with whom she had her daughter, Julia. Like the Rzeszowski family she had come to Jersey looking for work. Polish residents make up a significant minority on the island - close to 10% of the population.
Relatives of Marek and Izabela have spoken of the deep pain and incomprehension following the killings. The couple had been together for many years and they knew Damian well but say there was no hint that he was capable of such violence. They now hope that he will be forced to serve a lengthy prison sentence in England. They do not want him to return to Poland.
These were the first murders on Jersey for seven years and caused deep shock on the small island.
There will be relief that the man responsible has now been jailed, but sadness that such a savage attack could have happened in their community.