The cross-examination of a boy who was sexually abused by a teacher at a Perth private school was so traumatising other parents were deterred from reporting abuse, his mother says.
The Royal Commission into Institutional Responses to Child Sexual Abuse has been examining how victims fare when they give evidence in the trials of their abusers.
In the first part of a two-part hearing, the commission is exploring how different jurisdictions make judicial decisions on the admission of tendency evidence - that is evidence on an alleged abuser's likelihood to sexually molest children.
It has heard from survivor witnesses and Crown prosecutors involved in trials in NSW, Victoria, Queensland and Western Australia that when judges rule tendency and coincidence evidence is not admissible, an abuse victim can end up being the only complainant in a separate trial.
In that scenario it is their word against the word of the accused, who is often backed by a high-powered legal team.
In these trials the jurors never get the full back story and the chance of conviction has been shown to be lower.
The commission has heard every jurisdiction differs when it comes to tendency evidence and the differences can impact on witnesses.
On Thursday the mother of CDX, a boy who was groomed and sexually assaulted when he started at the Perth private school in 2000, said her whole family found the criminal justice process devastating.
She said the original cross-examination of her son and other young adult witnesses was so traumatising that a number of friends who witnessed it told her they would never report to police if their child disclosed they had been sexually abused.
It was also never fully explained to the family what was happening when the teacher, who was convicted in 2010 and jailed for five years, appealed his case and a retrial was needed.
Earlier on Thursday the commission heard children as young as seven in a Queensland home for boys were terrorised and sexually abused by a trainee police officer, but a jury never got to hear the full story.
Dennis Dodt was a ward of state at the Enoggera Boys Home in Brisbane in the 60s where he was indecently assaulted by Graham Noyes, a volunteer at the home and a trainee policeman.
Multiple complaints against Noyes, a former police officer who became a UN peacekeeper in Cyprus, were tried separately and he was acquitted in three trials but found guilty in a fourth.
Mr Dodt said on Thursday he felt "undermined and disbelieved" when in 2003 the Queensland DPP persuaded him to drop his complaint on the grounds that another conviction for a similar complaint was unlikely to succeed.
The hearing continues on Friday.