The high-profile barrister Bret Walker SC has argued jurors who convicted Cardinal George Pell of child sexual abuse were wrong to reject arguments from his defence about the improbability of the offending occurring, saying jurors should have held reasonable doubt about whether Pell abused two choir boys even if they believed his victim.

On Wednesday Pell’s final chance of appealing his verdict began before the full high court bench of seven justices in Canberra. The court is yet to grant Pell leave to appeal his conviction – first, it heard arguments from Walker as to why the appeal should be allowed. It may grant or deny the appeal at any time, with Thursday also set aside for the case.

Outside the court, Pell supporters who arrived together on a bus gathered holding crosses and a sign that read “We are praying for you Papa”. A victim advocate held up a sign that read “Go to hell Pell”.

Walker’s central argument was Pell did not have the time or opportunity to offend. While he accepted jurors found the complainant believable and compelling, he argued this was beside the point.

“The true question is not ‘Do I believe the complainant’ but whether, ‘having believed the complainant, is there any reasonable doubt as to [Pell’s] guilt?’,” he said.

Walker told the bench, led by the chief justice, Susan Kiefel, that the jury’s perception of the complainant’s credibility should not have alone persuaded them of Pell’s guilt beyond reasonable doubt.

“It is an extreme fallacy for anyone to assume the credibility of the complainant will supply an answer to reasonable doubt raised via evidence to which the complainant says nothing,” Walker said.

Doubt “… could not be eliminated [just] because the jury had manifestly been impressed by the complaint”, Walker said. He said this was because the complainant’s evidence, even if it was impressive and believable, did not address questions of doubt raised by the defence, such as a lack of opportunity for the offending to have occurred. There had been evidence Pell would have been greeting parishioners on the church steps when the offending occurred, he said, as well as evidence that the church corridors and sacristy were a “hive of activity” after mass.

Quick Guide Who is George Pell and what has he been convicted of? Show Who is Cardinal George Pell? Pell was essentially the treasurer of the Vatican and the Holy See in Rome. He has also been a longtime confidant to Pope Francis. Before his appointment to the Vatican in 2014, Pell held senior positions within the Catholic church in Australia, including as the archbishop of Sydney and the archbishop of Melbourne. He is known for his staunch conservativism on issues including marriage equality and abortion. Pell is now also the highest-ranking Catholic official in the world to have been convicted of child sexual abuse. What has he been convicted of? In June 2017 Pell was charged with child sexual assault offences by Australian police. Pell took leave from the Vatican and stood aside from his position to return to Australia and fight the charges, which were split into two trials. The first group related to offending in 1996 at St Patrick’s Cathedral in Melbourne when he was archbishop. The second group related to alleged offending in a swimming pool while he was a priest in the regional Victorian town of Ballarat in the 1970s. The cathedral trial was held in August and resulted in a hung jury. A mistrial was declared and the trial was held a second time, beginning in November. On 11 December the jury returned a verdict of guilty on five charges; one count of sexual penetration of a child under the age of 16 and four counts of indecent assault of a child under the age of 16. The convictions relate to Pell’s offending against two 13-year-old choirboys. Why are the details only coming out now? A suppression order was in place so that jurors in the trial of the second group of alleged offences would not be prejudiced by reporting of the first trial. But the swimming pool charges were dropped by prosecutors on 26 February after evidence they were relying on to build their case was deemed inadmissible by the judge. As a result the suppression order was lifted.

What is happening now? Pell continues to appeal his conviction. In March 2019, the full bench of the high court in Canberra reserved its decision about whether to grant him special leave to appeal his case for a final time

The court also grappled with whether Victorian appellant court judges, who dismissed Pell’s first appeal by a majority of two-to-one, may have been unduly influenced by the complainant’s testimony by watching a recorded video of it rather than just reading the transcript. Walker said it may have led the judges who dismissed the appeal to give too much weight to the complainant’s evidence rather the evidence from the trial in its entirety.

Pell’s master of ceremonies at the time of the offending, Charles Portelli, gave evidence during the trial that Pell would usually remain on the front steps of the cathedral after mass greeting parishioners for anywhere up to 20 minutes. If this were the case, Walker said, there would be no opportunity for Pell to offend in the sacristy. Prosecutors argued at trial that while standing on the steps became Pell’s custom, it was not yet custom after he first became Archbishop in 1996, and other witnesses gave evidence that there were occasions when this meet and greet might be skipped or cut short.

Walker told the high court the prosecution had not discredited Portelli’s evidence. His evidence was “material on the basis of which you can not eliminate the possibility that the archbishop was on the front steps.” That “forensically” put a “full-stop” on any chance to offend, Walker said. “That’s another point that says it was not open to find guilt, on the balance, beyond reasonable doubt,” he said.

Justice Michelle Gordon asked Walker: “What is the evidence giving rise to the possibility that he was on the front steps?”

Walker responded that evidence Portelli and others gave “shows at least the possibility that he was with the archbishop meeting and greeting at the opposite end of the cathedral where he had to be at the time of the alleged offending”.

He brought up Portelli’s description of the robes Pell wore when he was Archbishop, including Portelli’s demonstration of how the cincture around the waist was tied. Pell’s defence team argued during trial that it would have been “impossible” for Pell to manoeuvre the robes in such a way to expose his penis and assault the boys.

The jury had before them uncontested evidence that the robes could not be manoeuvred in a certain way, Walker said, to which Justice Bell replied: “But the jury did have the robes as an exhibit in the jury room”.

Walker responded: “Unfortunately none of us knows what experiments that led to”.

Pell, 78, is serving a prison sentence of six years, with a non-parole period of three years and eight months. In December 2018 a jury found him guilty on four counts of an indecent act with a child under the age of 16 and one count of sexual penetration with a child under the age of 16.

They believed Pell sexually assaulted two choirboys in the priest’s sacristy after Sunday solemn mass at St Patrick’s Cathedral in Melbourne in 1996. Pell orally raped one of the boys, the complainant in the case, during this incident and indecently assaulted both of them. Pell offended a second time against the complainant one month later, when he grabbed the boy’s genitals in a church corridor, once more after Sunday solemn mass.

By the time the complainant spoke to police in June 2015, the other victim had died from an accidental heroin overdose at the age of 30.

The hearing will continue Thursday when the director of the Office of Public Prosecutions, Kerri Judd QC, will respond to Walker’s arguments.