The father of the man, who has died, is gutted by the High Court's decision to release the cardinal, his lawyer Lisa Flynn says.

"I'm disgusted," he said through Ms Flynn on Tuesday.

"He is furious. The man he believes is responsible for sexually abusing his son was convicted by a unanimous jury, only to have that decision overturned today, allowing George Pell to walk free from jail."

She said her client had lost faith in the justice system and was shocked over the decision.

"He is heartbroken for the surviving victim who stuck his neck out by coming forward to tell his story but was ultimately let down by a legal process that forced him to relive his pain and trauma for no benefit."

The remaining accuser who gave evidence at Cardinal Pell's trial was an "upstanding citizen" who the jury believed.

"[He] had nothing to gain from speaking out other than to protect other children from the pain and suffering he has to live with on a daily basis," the statement reads.

The surviving choirboy, Witness J, is expected to issue a statement on Wednesday, according to his legal team.

Family members of another accuser who claimed he was sexually assaulted at a Victorian pool have also thrown their support behind the witness.

Those allegations, however, never went to trial because of insufficient evidence.

"It is more important than ever that they continue to speak their truth and hold to account both perpetrators and institutions. Our thoughts are with J, his family and friends. You are not alone, you were believed," they said in a statement.

The deceased choirboy's father continues to believe his son was a victim of sexual abuse at the hands of the cardinal, Ms Flynn said.

"We will continue to pursue a civil claim on behalf of our client despite the High Court's ruling today," she said.

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Australian Associated Press