Two brothers repeatedly stabbed their mother's partner after they thought he had attacked her on Halloween.
Christopher McLaughlin, 26, and his sibling Darren, 23, attacked Kevin McCartney in his West Dunbartonshire home.
The pair had earlier spotted marks on Isobel McLaughlin's neck and thought the 48-year-old was responsible.
So the duo went to his home and stabbed the qualified intensive care nurse at his home in Alexandria a total of 13 times.
Mr McCartney later died after receiving "catastrophic" medical treatment at the Royal Alexandra Hospital in Paisley and the Southern General in Glasgow following the attack on October 31, 2010.
At the High Court in Edinburgh on Monday, Lady Stacey jailed them for four years each and ordered that the McLaughlins be supervised by the authorities for two years following their release from prison.
Prosecutors agreed to drop the murder charge in return for the pair pleading guilty to the lesser offence.
During that hearing, the court heard how Mr McCartney and Mrs McLaughlin had spent the evening of October 30, 2010, drinking in a nearby pub. They had an argument before leaving the bar and returning to Mr McCartney's flat.
Prosecutor Pino di Emidio said Mr McCartney called police in the early hours of October 31 to say the McLaughlins were kicking the door of his flat. It is believed the brothers gained entry and stabbed Mr McCartney, who also identified the brothers during the telephone call to the emergency services.
His condition worsened at the Southern General due to a perforation of the bowel that had not been spotted by medics at the RAH. On November 9, it was discovered he had fluid in his lung.
A particular type of chest drain was inserted where there was "very little margin for error". But within minutes, Mr McCartney collapsed and died.
Medical experts later reviewed what happened and one stated that the chest drain was "inappropriate". The Southern General also investigated the treatment and concluded there were "several missed opportunities" in how Mr McCartney was cared for.
A doctor from Edinburgh Royal Infirmary described the insertion of the chest drain as "catastrophic".
On Monday, first offender Christopher McLaughlin's advocate Ian Duguid QC said his client was sorry for the hurt he had caused Mr McCartney's family. Darren McLaughlin's counsel, Edward Targowski QC, said the joiner, another first offender, accepted his guilt in the matter and was prepared to be sent to prison.
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