Girls as young as 18 months who came into contact with the NSW child welfare authorities from the 1930s onwards were routinely tested for venereal disease and evidence of sexual activity.
If they were found, on the basis of a spurious vaginal examination, to have been sexually active, from the age of 10 upwards they could be sent to the Parramatta Girls Home where they were exposed to "state-sanctioned rape" perpetrated by doctors, supervising staff and other inmates.
The notorious detention centre for girls, which shut down after public outcry in 1974, is the focus of hearings for the Royal Commission on Institutional Responses to Child Sexual Abuse starting on Wednesday.
Harrowing testimony is expected as 10 women, who were among the thousands detained in the
home or at the associated Institution for Girls at Hay during the period of 1950-1974, take the stand to tell their stories.
In the 2005 book Orphans of the Living by Joanna Penglase, a NSW departmental field officer explained how girls picked up on vague grounds of being "exposed to moral danger" were subjected to vaginal examinations.
If the doctor could insert three fingers into your vagina "then you'd been highly promiscuous" the officer said, describing the procedure as "just a straight assault".
Despite having no scientific basis, this test could be used to assign a girl to the Parramatta home, wrote Dr Penglase, who called it state-sanctioned rape.
"Regardless of whether she claimed she had been abused by a parent or foster carer or [someone else], she was seen to be guilty," said Bonney Djuric, who was sent to the Parramatta home in 1970 and founded a support network for former inmates, Parragirls, in 2006.
"For many girls having this examination was essentially their first sexual experience, if you can call it that," Ms Djuric said.
"Being raped by having a metal object inserted is something you never forget."
Ms Djuric, an author of two books on the Parramatta home and the Institution for Girls, has documented first-hand accounts of girls being sexually abused at the institutions from the 1930s onwards by superintendents and staff, after being groomed for sex or as part of violent punishment.
There were also "many cases where girls were essentially gang-raped by other girls within the institution", she said.
"That was commonly known by all of us," Ms Djuric said.
"It was a great fear that we all held."
The Parramatta and Hay female detention facilities will be the seventh case study heard by the commission.
The commission is due to publish interim findings at the end of June on the case studies it has heard to date, including those on Scouts Australia and the Hunter Aboriginal Children's Service, YMCA NSW, the Anglican North Coast Children's Home, the Catholic Church's Towards Healing protocol, the Salvation Army (eastern territory) and a Catholic primary school in Toowoomba.
For more information, go to: smh.com.au/royalcommission.Lifeline 131114 beyondblue 1300 224 636.