A forensic expert has questioned the reliability of scientific testing in the case of Tasmanian killer Susan Neill-Fraser, as part of her last-ditch bid for freedom.
Neill-Fraser is serving a 23-year jail sentence for murdering partner Bob Chappell, who disappeared from the couple's yacht at Sandy Bay on Australia Day 2009.
His body has never been found.
Neill-Fraser was in 2010 found guilty of bludgeoning Mr Chappell with an unknown object, winching his body onto the deck of the boat before dumping it in the River Derwent.
But she's always maintained her innocence and has launched an appeal bid under new Tasmania law which requires her to provide "fresh and compelling" evidence to warrant a re-trial.
On Thursday, the Hobart Supreme Court heard from former WA Police forensic expert Mark Reynolds, who reviewed forensic testing of the dinghy.
He said 16 swabs from seven locations failed to show human blood on the dinghy.
"(There was) no chemistry confirmatory testing to see that there was blood on the dinghy," Mr Reynolds said.
"In my opinion, it's not blood. It's not human blood."
But under cross-examination from Daryl Coates SC, Mr Reynolds agreed the jury at the original trial hadn't heard there was blood on the dinghy.
"Would you accept there is nothing in this report that is fresh and could not have been made at the point of the trial?" Mr Coates asked.
"Yes, I would agree," Mr Reynolds replied.
Neill-Fraser' lawyers have indicated they may call more witnesses to respond to fresh material.
The drawn-out hearing is expected to hear from one witness on Friday, with the matter to resume again in late June.
Australian Associated Press