An Adelaide man is again seeking to challenge his 1994 conviction for drowning his fiancee in a move supported by Gordon Wood, who was eventually acquitted of murdering his girlfriend.

Henry Keogh’s lawyers are arguing that fresh evidence – including the possibility his fiancee may have suffered an extreme allergic reaction – undermined his conviction.

Keogh, who says her death was a terrible accident, is serving a minimum 25-year jail term for murdering Anna-Jane Cheney in the bathtub of their home in March 1994.

He has lost numerous appeals, but on Monday his lawyer, Marie Shaw QC, began a landmark challenge – based on new SA legislation – arguing there was fresh and compelling evidence in the case.

Justice Kevin Nicholson will decide if she has an arguable case to warrant a full hearing into the conviction.

Monday’s hearing was watched by Mr Wood, who spent three years behind bars after being convicted of murdering Caroline Byrne whose body was found at the bottom of an infamous Sydney suicide spot in 1995.

He was later acquitted by the NSW Court of Criminal Appeal and has visited Keogh in prison.

Mr Wood refused to speak to some journalists outside the Adelaide court because of his pending legal actions against media outlets, but his sister Jackie Schmidt said her brother supported Keogh.

“He has a passionate interest in potential miscarriages of justice in cases similar to his,” she said.

He was particularly interested in cases where evidence “masquerading as scientific” had been given more weight that it should have been, Ms Schmidt added.

Prosecutors had claimed Keogh drowned Ms Cheney by grabbing her legs and lifting them up over her head.

Referring to an alleged grip mark on her leg, Ms Shaw said there was now evidence from a sample of her tissue that showed the bruise was at least three to four days old at the time of her death.

She said that at the trial the crown had “pitched” the submission that the jury could exclude accidental drowning, referring to the grip mark.

The court was also told of a new report suggesting Ms Cheney had been prescribed and used the drug Hismanal some time before her death.

Associate Professor Anthony Thomas has suggested this drug could have caused an allergic reaction that raised the possibility of anaphylactic shock being the cause of death.

The hearing seeking permission to appeal is expected to last five days.