Cardinal George Pell may have become the target of false sexual offence allegations to punish him for not having prevented the sexual abuse of children, his defence barrister has told a court.

Robert Richter QC has described complaints made against Cardinal Pell as "impossible" and the complainants behind them as "unreliable" as he tried to persuade a magistrate not to commit Australia's most senior Catholic cleric to stand trial.

Instead, Mr Richter told the hearing at the Melbourne Magistrates Court that all the charges faced by the 76-year-old should be thrown out.

"Whether the allegations are the product of fantasy, the product of some mental problems … or just pure invention in order to punish the representative of the Catholic Church in this country for not stopping abuse by others of children," he said.

Mr Richter said some of the complainants had been sexually abused by other priests who had since died, therefore offering them no recourse.

"Cardinal Pell representing the face of the Catholic Church … had been the obvious target of allegations that are not true, but are designed to punish him for not having prevented sexual abuse of young children," he said.

As the "face" of the church, Cardinal Pell was an obvious target, Mr Richter said. ( ABC News: Karen Percy )

The comments were later rejected by prosecutor Mark Gibson SC as a "theory and … nothing more than a theory".

The court heard the most serious allegations made against Cardinal Pell related to alleged sexual offending in Ballarat in the 1970s and at St Patrick's Cathedral in Melbourne in the 1990s.

Mr Richter told the magistrate their complaints were "impossible" and "ought to be discharged without batting an eyelid".

He said the balance of the charges should also be thrown out.

"The complainants are unreliable, the complainants have made prior statements that are inconsistent or subsequent statements that are inconsistent," Mr Richter said.

"Their credibility has been damaged to a point where … that shot is not worth the powder of proceeding to a charge or proceeding to a trial."

Conflicting evidence 'not a defect'

Magistrate Belinda Wallington said she believed a person should be committed to stand trial unless there was a "fundamental defect" in the evidence.

"I think issues of credibility and reliability are matters for a jury except where you get to a point where the credibility is effectively annihilated," she said.

Mr Richter agreed and contended that some of the complainants just could not be believed.

He also hit out at the police investigation, again criticising Victoria Police for establishing an operation to investigate Cardinal Pell before any complaints had been made against him.

Prosecutor Mark Gibson argued conflicting evidence did not amount to a defect. ( AAP: Stefan Postles )

Mr Richter argued that detectives had not properly investigated the allegations and instead acted under the "current political correctness in attitudes" which meant victims were always believed without their account being tested.

"There is simply no supporting evidence for these allegations," he said.

"Multiplying unreliable witnesses does not lead to a conclusion that there is a strong and probable cause to commit."

But Mr Gibson SC said none of the complainants resiled from their allegations.

He said conflicting evidence did not amount to a "defect in the evidence".

"It does not fundamentally impact on the reliability of the complainants' evidence," Mr Gibson said.

'Damning character assassination'

Cardinal Pell took leave from his position at the Vatican to return to Australia to fight the charges last year.

Mr Richter said he returned voluntarily instead of claiming diplomatic immunity and fighting extradition.

"He has given a full and complete account when asked questions, he may have overlooked things, he may have forgotten things … he is consistent and he is adamant that none of these instances took place," he said.

Mr Richter also took aim at ABC journalist Louise Milligan for what he described as the "disgraceful publication" of her book detailing allegations made against Cardinal Pell.

He said the book was a "damning character assassination" which had damaged Cardinal Pell's prospect of a fair trial and should be taken into account when deciding whether to commit him on "trifling charges".

Ms Wallington will hand down her decision on whether to commit Cardinal Pell to stand trial on May 1.

Editor's note: On Tuesday April 7, 2020, the High Court in a unanimous decision upheld Cardinal Pell's appeal and quashed his convictions on all five charges.