A class action on behalf of current and former Manus Island detainees will begin in Melbourne on Wednesday.
A class action seeking damages for people detained at the Manus Island immigration detention centre will begin this week.
Fifty current and former Manus Island detainees, including 41 people who remain in Papua New Guinea, will give evidence as part of Australia's largest trial concerning immigration detention.
The six-month trial was scheduled to start in the Victorian Supreme Court on Monday, but a judge granted a request by all parties to delay it until Wednesday.
The 1905 class action group members are seeking compensation for alleged physical and psychological injuries they argue they suffered as a result of the conditions in which they were held on Manus Island.
The current and former detainees want additional damages for false imprisonment after the PNG Supreme Court ruled the detention of asylum seekers on Manus Island was unconstitutional.
The Australian government and the companies that have managed the Manus Island Regional Processing Centre, G4S Australia and Broadspectrum (formerly Transfield Services), deny the claims.
The judge-only trial will hear from 41 current or former Manus Island detainees who remain in Papua New Guinea, as well as 11 former Manus detainees who are currently being held in some form of detention in Australia.
The first detainee to give evidence is expected to be lead plaintiff Iranian-born Majid Karami Kamasaee, who spent 10 months on Manus Island and now lives in community detention in Melbourne while he awaits a decision on his refugee status.
Justice Michael McDonald on Monday agreed to delay the opening of the trial until Wednesday, after the parties were involved in further pre-trial applications on Friday.
The Manus Island centre is due to close on October 31.