I suspect that is because there are so many cases where husbands kill wives that to suggest they don’t would be scoffed at, but this defense is REALLY hanging their hats on the common belief that fathers do not kill their sons.
So, many defense witnesses have talked of their memorable love and affection for Paul in the Defense team’s hope that jurors will project those into their concept of the relationship between Alex and Paul.
But, if Alex loved Paul, he’d have disciplined him. By that I don’t mean anything like spanking or punishment, I mean “making Paul a disciple of his father’s own good character and behavior.” That is, teaching - by example and by instruction - Paul how to be in the world to live a good life. Not an indulged and self-destructive life, but a life built on service to good relationships, development of a worthy vocation, investment of self into a larger community.
But Alex didn’t have it in him. He only had indulgence. Let Paul have whatever he wanted as an extension of Alex having whatever he wanted. And when indulging Paul resulted in consequences which threatened to expose the full extent to which Alex indulged himself (cheating and stealing from others), Paul lost his utility to Alex and he didn’t want Paul as an extension of himself anymore.
So, he eliminated Paul and used the tragedy to bask in the sympathy that came his way after.
The common belief that fathers don’t kill their sons cannot be applied to Alex because he didn’t earn that presumption like most fathers do.