It will also have a devastating impact on the healing and mental health of sexual assault survivors, they claim.

However, some legal experts, including the ACT Director of Public Prosecutions, argue that the Pell decision has in no way changed the law.

Since being handed down on April 7, the Pell judgment has been cited in 65 cases in Australian courts, almost all of these in matters before a court of appeal.

It has so far been used in four cases in ACT courts and was central in July to convicted child sex offender Robert Glen Sirl, 49, having two convictions overturned after an alleged violent rape.

One of the other ACT cases that cited Pell also saw an appellant succeed in getting two rape convictions quashed. Another man failed in getting his convictions overturned and the fourth case saw an appeal succeed, but it did not involve sexual offences.

Sirl was accused of raping a woman who had attended his home to buy drugs from him.

The woman was allegedly attacked with a sharp bladed object which caused such significant injuries she lost almost half of her blood volume and required emergency surgery.

She initially told police she had been on a Tinder date, but eventually claimed Sirl was responsible and said she had been too scared to name him as her attacker.

A jury found Sirl guilty of rape and inflicting grievous bodily harm, but three judges concluded on appeal that "there was a significant possibility" he was innocent, quoting from the Pell decision.

The decision centred around the fact that while the jury had found the complainant a credible and believable witness, other evidence presented during the trial had been inconsistent with the woman's version of events.

This is again crucially similar to the Pell case, where the jury found the alleged victim to present a compelling and believable story of what he said happened to him in the sacristy of St Patrick's Cathedral in Melbourne all those years prior.

But because of other evidence, namely unchallenged witnesses who questioned the likelihood that Cardinal Pell could have abused the boys in the manner described after a Sunday mass, the High Court found the jury should have entertained a doubt as to the church leader's guilt.

In the Sirl case, the ACT Court of Appeal agreed with his lawyers that three other scenarios could not be ruled out. These were that the woman had suffered her injuries during consensual sex with Sirl, that someone else had assaulted the woman in the time between her having consensual sex with Sirl and calling an ambulance, or that the woman had inflicted her own injuries.

Swinburne University Law School lecturer Rachael Burgin, who is also chair of Rape and Sexual Assault Research and Advocacy, holds deep concerns about the lasting impact the Pell decision will have on survivors of sexual abuse.

"Survivors aren't stupid. They are very aware of the criminal justice system. They are very aware they are not believed. They are very aware it is an absolute uphill battle," Dr Burgin says.

"It's not just trial outcomes and appeals this will impact. Down the line we will start seeing fewer cases being prosecuted, fewer cases being investigated by police. It will have a flow-on effect all the way back to the decision whether to report or not."

She argues the decisions to acquit Pell and Sirl ignore what we know of how traumatic events can affect memory, causing it to be hazy or incomplete, and the criminal justice system needs to be adaptable to that.

In a system that is already exceedingly difficult to navigate for survivors, Dr Burgin believes Pell further "stacks the deck" against victims, that offenders will be emboldened to appeal and that the evidence from survivors will be given even less weight by the courts.

In addition, Dr Burgin says these decisions act to further undermine the jury system which is so crucial to Australia's legal system.

But ACT Director of Public Prosecutions Shane Drumgold SC disagrees, and is keen to argue that the Pell judgment has not, as Sirl's counsel put it, "changed the landscape".

"Any academic opinion suggesting the Pell case has significantly changed the legal landscape is based on a superficial analysis and is incorrect," Mr Drumgold says.

"The Pell decision in no way changed the law, nor the approach to determining appeals of this nature.

"The decision did not create any new legal precedent, nor does the outcome in that case make it more or less likely that convictions will be sustained on appeal."

Mr Drumgold says that in fact, the Pell decision is further affirmation of legal principles that have been in place for more than a quarter of a century.

The relevant test that courts must apply in such appeals was stated in a 1994 decision, when the High Court acquitted a man who had been found guilty by a jury of raping and indecently assaulting his teenage daughter.

Mr Drumgold stresses that the court applied the test in the Pell case and did not change it.

Essentially, the territory's top prosecutor says, the test requires appeal judges to examine all the evidence presented to a jury as part of a review into whether it was reasonable for the jury to have found the accused guilty.

The judges begin this task assuming that the jury must have considered the evidence against the accused to be credible and reliable.

However, they look for inconsistencies or discrepancies to determine whether or not jurors, regardless of their confidence in any incriminating evidence, should still have finished deliberations with doubt in their minds.

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"The High Court's analysis and the ultimate result in Pell was based upon the application of the settled test to the particular facts and evidence in that case, rather than any new tests," Mr Drumgold says.

"The result is in no way determinative of the outcomes of appeals against conviction in other cases.

"Like all appeals of this nature, the outcome depends upon the specific circumstances and evidence in each case.

"As the law and principles in this area remain settled and unchanged, there is no proper reason for the High Court's decision in Pell to affect the legal outcomes of conviction appeals."

However, Dr Burgin argues the implications of Pell go far beyond matters decided in the courtroom, and the real impacts will be felt in the day-to-day lives of survivors.

Particularly as the Pell decision was so well-publicised and is a contemporary example of the odds against complainants, Dr Burgin believes this will impact on victims in a way previous case law may not have.

"The Pell case is now the ultimate precedent on this issue," she says.

"The biggest impact is it's something the community now can see and understand what is happening. It's opened the floodgates further. The prospect of a harder conviction and the likelihood of going to appeal will mean less people will report.

"Not even not reporting, but not seeking help by other means. There will be people that don't feel comfortable sharing with family and friends, sharing with a counsellor.

"The criminal justice system does not exist in a vacuum, and these decisions have a big impact on how survivors live their lives."