David Mahon stabbed Dean Fitzpatrick outside his apartment at Burnell Square, Northern Cross on the Malahide road.
David Mahon is married to Audrey Fitzpatrick, the mother of the man he killed during an argument over a water bottle he'd stolen from his bike.
At his sentence hearing earlier this month, Audrey's Victim Impact Statement said she's already forgiven her husband but that it wouldn't be forgotten.
The 45-year-old admitted holding the knife that killed him but claimed it was accident, and even suggested he'd wanted to walk onto the blade.
Dean's death isn't the first tragedy to befall the family. His sister Amy hasn't been seen since she went missing in Spain in 2008.
They'd moved over there with Mr. Mahon and Audrey four years beforehand.
He was cleared of murder last month but convicted of manslaughter and has been in custody ever since.
He'll find out later today what sentence he'll have to serve.
