Barry McLean, a former pupil of Burntisland Primary and Balwearie High School, left behind a baby son when he died on May 28 2011, aged 27.
Sean Kitchener admitted “poking” Barry with a kitchen knife but made a plea of self-defence at the High Court in 2012 and was cleared of murder.
The family want the case reinvestigated and tougher penalties introduced, which they believe will reduce knife crime by “setting an example to those who carry out such horrific acts”.
Last month Barry’s father, Alan, told MSPs of the “everlasting pain” his family suffer. He gave evidence on a petition he has lodged at the Scottish Parliament asking the government to consider giving judges the ability to refer “irrational, unsupported or unbelievable” verdicts of acquittal to the appeal court for review.
He wants to see the proposal turned into new legislation – to be known as Barry’s Law – and asked MSPs to back his call for trial judges to have the power to refer “perverse acquittal” jury verdicts to the appeal court.
He also criticised the current system for selecting jurors as a “lottery”, which made it possible for “incompetent” people to be chosen, and said a suitability test should be employed.
Mr McLean told The Courier yesterday: “It’s four years since our handsome and precious son was killed. His killer still walks the streets, getting on with his own life as if he has never done anything wrong.
“How can our justice system allow someone to admit to the worst crime imaginable and allow them to walk free from a High Court with no form of punishment at all?
“Our system is clearly geared for the criminal and we need radical changes to provide strong deterrents, as we currently live in an unsafe society. Not a week goes by without hearing on the radio/television of someone being a victim to knife crime.”