Cardinal George Pell's barrister has accused police of failing to follow guidelines for investigating prominent people as the senior cleric fights historical sex offence charges.
Pell is the highest-ranking Catholic official to be charged with historical sexual offences involving multiple complainants, which he denies.
Pope Francis' former finance minister was charged in June of a year ago with sexually abusing multiple people in his Australian home state of Victoria.
Pell, in a beige jacket on top of a black shirt with a clerical collar, arrived by vehicle and was escorted by dozens of police as he made his way up the steps and into the Melbourne Magistrates Court.
Wallington replied: "No, they're also there for vulnerable and traumatized people".
"It is a guide to police about how to fairly investigate claims against prominent people", he told the court.
In court, Cardinal Pell's barrister Robert Richter QC took issue with an initiative that allows a trained Labrador to comfort those giving evidence during the hearing.
Mr Richter questioned whether police had taken into account the 21 witness statements the defence had provided, which were favourable to the cardinal.
"These documents are certainly relevant to the alleged offenses".
"We say that wasn't followed because there was a presumption of guilt", he said.
The cardinal, 76, arrived at Melbourne Magistrates Court on Monday accompanied by several police officers, reports CNN.
"For the avoidance of doubt and because of the interest, I might indicate that Cardinal Pell pleads not guilty to all charges and will maintain the presumed innocence that he has", Richter said in July.
Pell was archbishop of Melbourne before working as Prefect of the Secretariat of the Economy, the Vatican's finance director.
The court was open to the public for 25 minutes before adjourning until Monday afternoon, when it will be closed as the first complainant begins giving evidence.
Critics argue that the Church has done little to bring perpetrators to justice, despite Pope Francis pledging "zero tolerance" in 2014 on sexual abuse.
Pell's lawyers told the court last month that the current criminal charges stemmed from publicity surrounding the Royal Commission into Institutional Responses to Child Sexual Abuse.
Pell appeared before it three times, once in person and twice via video-link from Rome over his dealings with paedophile priests in Victoria state in the 1970s.