"Our evidence for the hearing will outline the problems with current state redress processes, especially the lack of transparency, accountability and independence," Hill, whose firm represents about 1400 survivors, said.
"It's a broken, overwhelmed system of the state investigating itself, which is impossible to do so fairly."
Evidence would include a proposal there be "a process independent of the state, empowered to provide redress which meaningfully improves the lives of survivors".
"If we don't do this, we will continue the generational harm of abuse in state care which we still see today."
Wellington man Keith Wiffin, who was sexually and physically abused in state care in the 1970s, and has been seeking redress since 2003, said the state had had ample opportunity to put things right.
"What lies at the heart of this ... all the belligerence we've had, is about the Crown wanting to protect the perceived civil liability above all else and to limit compensation to as close to zero as possible ... and for me that's why an independent body [needs to be] in place."
The 10-day hearings are the first of two planned. A second in October is for state entities' witnesses to talk about their redress processes.
The Royal Commission, which is looking into what happened to children, young people and vulnerable adults in state and faith-based care between 1950 and 1999, will ultimately make recommendations to the Governor-General in 2023 on how New Zealand can better look after those in its care.