Defence advocate Piet Botha told the Western Cape High Court on Tuesday that the State failed to prove its case beyond a reasonable doubt in the trial of triple murder accused Henri Van Breda.
He said the State's case was based on speculation, "inferences should be drawn from facts", and that evidence presented by the State was of "poor quality".
Twenty-three-year-old Van Breda has pleaded not guilty to three counts of murder, one of attempted murder and one of obstructing the ends of justice.
It is the State's case that he attacked his family with an axe, and that his sister Marli, who was 16 at the time, survived the attack - not as a result of a lesser attack, but rather because of a "miracle".
The attack in the family home in the De Zalze, Stellenbosch security estate in 2015 shocked the country, and the sensational trial has dominated headlines for more than 60 days.
The defence has its final stab at convincing the court of Van Breda's version, that a laughing, axe-wielding intruder was behind the attack, and that the "State did not prove its case beyond reasonable doubt".
Botha said "what the court needs to decide is the identity of the attackers".
He said there was an attempt by the State to create the impression that the Van Breda home was impenetrable, that nothing appeared to be stolen, there had been no breach of the perimeters, that a heated argument on January 26 from 10pm until midnight had preceded the attacks, and that unlike the rest of his family, Van Breda had suffered superficial injuries that were self-inflicted.
"One can speculate, one can say the dog was in the garage, one can say he smoked cigarettes while waiting for his sister to die.
"One can convince oneself that the State has made out a strong case. The onus is on the State, not on the accused, to prove its case.
"We submit that the conclusion cannot be that the State proved itself beyond doubt. The actual evidence points the other way, or at the very least creates reasonable doubt."
He said the accused had made a "good witness" and had not deviated from his version of events.
Botha argued that the circumstantial evidence presented by the State supported the accused's narrative and not the State's.
"The circumstantial evidence presented by the State to prove its case against the accused does not warrant, as the only reasonable inference, that the accused was the person who attacked his family."
African News Agency/ANA