"I can possibly forgive someone who has killed a person but I can never forgive this man for cutting up a body, hiding it in a container. It is the worst thing you can do to a human body."
Callaghan's father, Phillip Callaghan, said he and his son had not discussed the murder, although they wrote to each other every fortnight.
He had seen his son once in the past two years, in jail, and told the Herald he would continue to write to each other.
"You would be absolutely astounded ... he's a fantastic kid."
While refusing to share his own views on the murder, Mr Callaghan said he had not yet come to terms with it.
"I cannot come to grips with what happened ... we never discussed it."
Mr Callaghan said he was curious to see as to whether police would still charge the 32-year-old friend of Callaghan who first agreed to help, changed his mind, and eventually gave evidence against him with immunity from prosecution.