The murder of the Lin family was not a crime driven by "intense bitterness and hatred" but rather, a professional "cold-blooded slaughter", Robert Xie's defence says.
Xie's barrister Graham Turnbull SC took aim on Tuesday at several key allegations mounted by the crown against his client during the almost eight month-long Supreme Court trial.
Revisiting evidence of the crime scene at the North Epping home and the injuries inflicted on the five family members, Mr Turnbull suggested it showed the murders were "unemotional", "committed", "practised" and "professional".
"Rather than intense bitterness and hatred there is just cold-blooded slaughter," Mr Turnbull submitted.
He said the evidence suggested there was not a "single baulking at what had to be done".
The injuries inflicted upon 11-year-old Henry and nine-year-old Terry also showed they had put up a "struggle for life" reminiscent of a contest that was "profound, significant and driven by fear".
Mr Turnbull questioned why one would carry out the murders alone and while everyone was inside the house.
"If the intense bitterness and hatred is related to (Xie's brother-in-law) Min Lin ... why wouldn't you just bump him off on the way to the newsagency in the morning?"
The risk of carrying out the murders in the way Xie is accused of doing was "horrendous" and "just so unbelievable", Mr Turnbull added.
The crown argues Xie was filled with intense bitterness and hatred when he crept into the North Epping home of Min in the early hours of July 18, 2009, and - wielding a hammer - killed him, his wife Lily, Lily's sister Irene and his nephews Henry and Terry.
But Mr Turnbull challenged the idea that the hammer was a primary weapon, saying there were a series of fractures across the ridge of Min's head that could have been caused by a bar or flat object.
The trial continues.
