A leading justice advocate has expressed hope that the next premier of Western Australia will be more receptive to reforms than Mark McGowan.

Mr McGowan resigned in a bombshell announcement on Monday, midway through his second term in office, citing exhaustion.

"This week will be my final week. I've loved the challenge of solving problems, making decisions, getting outcomes, and helping people. But the truth is, I'm tired. Extremely tired. In fact, I'm exhausted," he said.

Megan Krakouer and her National Suicide Prevention & Trauma Recovery Project colleague Gerry Georgatos have collected testimony from hundreds of current and former Banksia Hill Detention Centre detainees for a class action.

She told National Indigenous Times on Monday that while she wished Mr McGowan "all the best in his future endeavours... his announcement is music to my ears".

"We may now finally get someone who will listen, hear and act to abate this incarceration crisis, particularly as it pertains to Banksia Hill Detention Centre," she said.

"We have lost too many young people to suicide. We have had too many young people spending prolonged periods in lockdowns in their cells and coming out worse than before they went in."

Ms Krakouer said it was important to note the courage of Aboriginal families taking a stand against the system.

"What we must remember is the voices of those who have been incarcerated have spoken out, spoken their truth, the mothers and the fathers of the children detained have spoken their truth. That is the strength of our people," she said.

"Let the incoming premier have strength, conviction, love, care and a deep understanding of human life, and know that many of our people did not have a shot from the beginning.

"It is time to end the incarceration cycle that continues to repress our people and destroy our lives."