A High Court ruling in a 46-year-old murder case has renewed calls for a royal commission into the discredited former chief forensic pathologist who performed the young victim's autopsy.

Dr Colin Manock's 27-year career as South Australia's top forensic pathologist saw him conduct thousands of autopsies and testify in hundreds of court cases.

Among those was the drowning murder of 15-year-old Deborah Leach, whose partially clothed body was found buried in seaweed at Taperoo beach in Adelaide's north-west in 1971.

Frits Van Beelen was imprisoned for 17 years for the murder of Deborah Leach. ( ABC )

Her convicted killer Frits Van Beelen, who admitted being on the mostly deserted beach that afternoon, has always maintained his innocence.

Among other evidence, Dr Manock's testimony as to the time of death formed part of the prosecution case against him.

Dr Manock estimated the time of her drowning based on "unscientific" analysis of the teenager's stomach contents, and testified that it could have been no later than 4:30pm when Van Beelen had left the beach.

The High Court agreed with Van Beelen's lawyers that Dr Manock's analysis was wrong, but dismissed Van Beelen's appeal because it couldn't be satisfied that amounted to a substantial miscarriage of justice.

However, the court's findings that the evidence discrediting Dr Manock's testimony amounted to fresh and compelling evidence has reignited calls for a full inquiry.

Van Beelen's lawyer Kevin Borick (right) wants an inquiry into cases involving evidence from Dr Colin Manock. ( ABC News: Loukas Founten )

Van Beelen's lawyer, Kevin Borick QC, is among those who want to see a proper investigation.

"All members of the High Court clearly found that the evidence given by Dr Manock about the time of death was wrong," Mr Borick said.

"The time must come when there is in effect a royal commission or a proper commission of inquiry into his conduct."

Dr Bob Moles, a respected legal academic at Flinders University, agreed there needed to be a thorough investigation.

"I think it's self-evident that when serious questions have been raised about a person in such an important position that these things should not be left to the vagaries of individual pieces of litigation through the courts," he said.

"It would be very sensible for the Government to set up a royal commission or a judicial inquiry so we can get to the bottom of this."

Findings could prompt new appeals, expert predicts

Dr Moles said it also needed to be established whether Dr Manock was ever qualified to hold his position.

"That is an issue that has not been raised in any of the legal proceedings so far under this new right of appeal," Dr Moles said.

"If it is in fact determined that Dr Manock is not properly qualified either as a pathologist or as an expert witness — and we believe that those options are open — then in fact all of the cases in which he's given evidence would be subject to challenge.

"On his own admission that's about 400 cases and also, if he's not properly qualified to conduct autopsies, then the 10,000 autopsies that he says he's conducted would all have to be reconsidered."

Evidence supplied by Dr Colin Manock was part of the case against Henry Keogh, whose conviction was overturned in 2014. ( ABC News )

Dr Moles said the High Court judgment, despite ruling against Van Beelen, contained important findings that may help others waiting to reopen their cases.

"It's a very interesting judgment for us because the Court of Appeal in South Australia had interpreted this new right of appeal in a way that made the test for leave to appeal very demanding," he said.

"The High Court has in fact toned that down a bit.

"The Court of Appeal in South Australia refused permission to appeal in the Van Beelen case, the High Court granted leave to appeal, they just decided that the particular point that was raised before the High Court wasn't sufficient for the appeal to be granted."

In a statement, Attorney-General John Rau said he was still considering the High Court judgment.

"I have not had the opportunity to consider the reasons for the judgement, but I am pleased with the outcome," he said.