The sex abuse survivor, who cannot be named for legal reasons, brought the case against Peter Comensoli, claiming the Catholic Archdiocese of Melbourne was vicariously liable for his abuse.

The victim said he felt like he was dead after Gannon first assaulted him - that the priest had murdered him and the little boy he used to be was gone forever.

He later contemplated suicide and abused alcohol as a way to numb his pain.

Gannon assaulted the victim on three occasions between 1968 and 1970 while the child was an altar boy and a pupil at a Catholic primary school in regional Victoria.

The former priest was sentenced for those crimes in 2009.

On one occasion, Gannon drove the boy down dirt roads out to a remote area, where he molested and raped him. At the time the boy was terrified Gannon would get a shovel, kill him and bury him.

The boy bled from the attack, and tried to hide it from his family in the following days.

On another occasion, Gannon's abuse only stopped when he was interrupted by another altar boy arriving at church.

The victim managed to escape Gannon's grasp on a third occasion when he lured him into a pump house with the promise of a cigarette.

Part of the victim's claim was that, in about 1960, Gannon sexually abused another young Catholic boy.

When the boy and his mother reported the abuse to a parish priest, he dismissed them and did nothing - essentially, on behalf of the archdiocese.

A Victorian judge on Thursday ruled the archdiocese's negligence was one of the causes of the boy's abuse, and therefore it was vicariously liable for it.

The judge assessed damages for the victim at more than $1.9 million, with interest and costs yet to be determined.

The victim's lawyer, Rightside Legal's Michael Magazanik, said the court decision was the first against the Melbourne archdiocese.

"My client is completely thrilled and delighted that he's held the church to account," Mr Magazanik said.

"It absolutely changes the game for other survivors of clerical abuse."

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Australian Associated Press