Child killer Dieter Pfennig has questioned the reliability of DNA evidence used to jail him for the murder of Adelaide schoolgirl Louise Bell more than 30 years ago.
Pfennig is appealing his guilty verdict arguing, that without the crucial DNA material, his conviction is unsafe and unsatisfactory.
He's serving a minimum 35-year jail term for the murder of the 10-year-old, who was taken from her bedroom at her parents' home in 1983, even though her body has never been found.
Pfennig was arrested in 2013 when DNA scientists in the Netherlands linked him to the dead girl's pyjama top, which was found folded on a neighbour's lawn not long after she went missing.
The DNA match was obtained from just two threads found on the clothing.
Defence counsel Paul Charman told the Court of Criminal Appeal on Wednesday the scientific evidence could not exclude the possibility that Pfennig's DNA had been transferred innocently, well before Louise disappeared.
He said this could have happened on a number of occasions given that Pfennig's daughter played in the same basketball team as Ms Bell, went to school with her and the pair came together at other times, including a pool party.
Mr Charman said exactly how the DNA was transferred was simply unknown.
"It was always unknown and doesn't exclude innocent transfer," he told the court.
Mr Charman said the prosecution also had to prove that the DNA was deposited on the pyjama top in the conduct of the crime, otherwise, the guilty verdict was unsafe.
But prosecutor Sandi McDonald told the appeal court the trial judge had rejected the notion that Pfennig's DNA was transferred in some convoluted manner, travelling from the former teacher to his daughter and then onto Louise.
Ms McDonald said the judge had determined that such a proposition was "fanciful" and was entitled to reach that conclusion on the basis of the evidence.
The appeal court has reserved its decision.