A former choirboy who accused Australian Cardinal George Pell of abusing him has said he accepts the top Vatican cleric's acquittal, but urged survivors of child sex abuse to keep coming forward.

A day after Australia's top court quashed Cardinal Pell's conviction and released him from jail, "Witness J" said he understood and accepted the court's verdict.

"There are a lot of checks and balances in the criminal justice system," the man, who cannot be named for legal reasons, said in a statement issued by his lawyer.

"I respect the decision of the High Court. I accept the outcome."

The court found that the jury that convicted the cleric of abusing Witness J and his friend, both 13 years old at the time, should have had a reasonable doubt about his guilt.

"It is difficult in child sexual abuse matters to satisfy a criminal court that the offending has occurred beyond the shadow of a doubt," Witness J said. "It is a very high standard to meet - a heavy burden."

Regardless, he said: "I would hate to think that one outcome of this case is that people are discouraged from reporting to the police.

"I would like to reassure child sexual abuse survivors that most people recognise the truth when they hear it."

As many activists expressed concern that Cardinal Pell's case would compound survivors' pain, Witness J also said he was doing "okay" and was relieved the years-long case was over.

Read more
Pell child sex abuse convictions overturned
Timeline of Cardinal Pell's child sex abuse case

"I have my ups and downs. The darkness is never far away. I am okay. I hope that everyone who has followed this case is okay," he said.

"This case does not define me. I am not the abuse I suffered as a child."

The former Vatican treasurer had steadfastly maintained his innocence throughout a high-profile and lengthy court process.

A jury had convicted Cardinal Pell of the offences in December 2018 before that decision was upheld by a three-judge panel in Victoria state's Court of Appeal last August, in a split 2-1 verdict.

Once the Vatican's third-ranking official, Cardinal Pell was jailed this year.

But Australia's High Court found there was "a significant possibility that an innocent person has been convicted because the evidence did not establish guilt to the requisite standard of proof".