A man convicted of murdering his wife with a hammer claims retested DNA evidence on the weapon would have been of "extreme importance" to his trial's jury.
Queensland man Andrew John Cobby was found guilty in a 2021 trial of beating and strangling his estranged wife Kym, 51, outside her Gold Coast hinterland home in November 2017.
Cobby represented himself before the Brisbane Court of Appeal on Tuesday and spent several hours presenting what he said were six grounds for his guilty verdict should not stand and he should get a retrial.
"Any and all fresh evidence, particularly in relation to forensic DNA, is of extreme importance ... what would the jury make of the evidence before us today? Only the jury can make that determination," Cobby said.
Cobby said DNA retesting of the hammer that was presented at trial as the murder weapon had cast doubt over its link to a man he was living with at the time of Ms Cobby's death.
The appeal justices were also shown pictures of the hammer which Cobby claimed showed that his housemate had incorrectly described its colour and shape.
Cobby, then aged 59, was sentenced to life imprisonment for what Justice Peter Callaghan said was a clearly premeditated and sickening crime.
He admitted being present during the attack on the woman he had married more than three decades earlier - although they mostly lived apart from 2003 - but denied being responsible.
Instead Cobby told police an unknown assailant was behind the killing, ambushing his wife as he was about to get into a red Chrysler he had borrowed.
During the appeal hearing, Matthew Hunt of the Queensland Health Forensic and Scientific Services DNA analysis unit, testified that the testing procedure had improved since the hammer and other exhibits were first tested.
"The fact that we have more confirmed information and also the changes to the program have caused the new analysis to be different to the previous one," Mr Hunt said.
Philip McCarthy KC told the appeal justices that the new DNA results for the hammer were not materially different from what was presented to the jury at trial, which was that Cobby's housemate's DNA was not found on the hammer.
"The evidence has largely remained unchanged ... one of the probabilities we are looking at is in the millions and millions for the likelihood someone was a (DNA) contributor," Mr McCarthy said.
Mr McCarthy said other new DNA evidence assisted the prosecution's case as Ms Cobby's DNA had now been identified on the hammer's claw with a high probability.
"The reliance of the Crown on the hammer is one strand amid 13 strands of evidence, one of which being that Cobby's clothing was saturated with the blood of his wife," Mr McCarthy said.
Appeal Justice Debra Mullins said the court would reserve its judgment for delivery at a later date.
