The judge will today begin summing up what David Bain's lawyers describe as "undoubtedly the most extraordinary case in New Zealand's history".
Justice Graham Panckhurst will direct the jury through the legal arguments before they decide whether to acquit Bain or return him to prison.
Bain's lawyer Michael Reed, QC, finished summing up the defence case yesterday, saying Bain's father, Robin Bain, murdered his family before turning the gun on himself.
The Crown alleges David Bain, 37, murdered his father, mother, two sisters and brother and used his paper run as an alibi before putting his bloodied clothes in the washing machine and calling police.
Mr Reed said Robin Bain had a bite mark, a bruise on his hand that was less than 12 hours old, and what one witness described as the appearance of blood under his fingernails.
He also said Robin had blood on his hands, including a splash of blood on the second finger of his right hand, on the index finger of his left hand and a smear on his little finger.
Only one blood sample was tested and then destroyed by police before the Privy Council appeal, he said.
"All of the other blood samples went to the grave with Robin Bain. If one of those samples on Robin turns out to be any of the children, particularly Stephen, then the Crown has no explanation of how the blood of Stephen got on to Robin."
Mr Reed also spoke of Robin Bain having a history of depression and being worried about his daughter Laniet - who was going to "blow the whistle" on an incestuous affair - and a marriage that was all but over.
"Who is the more likely person to be a homicidal maniac? Is it the nice friendly, jovial 22 year-old with a new girlfriend and dog, enjoying what he is doing ... Or is it this sad, sad father who is going downhill?"
Mr Reed said the Crown's case had taken a U-turn on Tuesday when prosecutor Kieran Raftery invited the jury to make a decision on the murderer based on evidence from Stephen Bain's room.
Mr Raftery had said to the jury: "Answer the question who killed Stephen and you've answered all five counts in this indictment."
He had said Stephen's fingerprints, along with Bain's, were found on the rifle after a bloody fight took place in Stephen's room before the 14-year-old lost his life.
But Mr Reed said there was very little blood on Bain, which showed he checked on his family members but did not shoot them.
He said there was no blood on Bain's glasses and very little on his white T-shirt, especially if he was wearing the V-neck jersey the Crown said he was.
Mr Reed also said there was no blood on the topside of Bain's socks or inside his running shoes and only a smear on his black running shorts, which is consistent with him kneeling to check on Stephen when he returned from his paper run to find his family dead.
Mr Reed said, "The tragedy for David is that David still loves his father. He's not the father that David knew all those years. He's a man that suddenly flipped."