Thousands of refugees who have been detained on Manus Island have been directed to claim compensation through Papua New Guinea's National Court.
The Supreme Court determined in 2016 that the refugees' detention was unconstitutional, but it decided in October that the question of compensation should be considered in the lower court.
The refugees' lawyer, Ben Lomai, said it would not be easy retrieving witnessed affidavits from so many men now spread all over the world.
But he said it was necessary to file an individual case for each refugee.
"Anyone that has passed through Manus Island is entitled to claim. It's up to them to give us the instructions," Dr Lomai said.
"So if we can get 1000, 1500 or even 2000 that have passed through, so long as we have their instructions, that's very important."
The affidavits need to witnessed by a notary public or a justice of the peace to be accepted by the National Court, the lawyer said.
About 70 affidavits have been filed so far, mainly from refugees in Port Moresby, he said.
In the new year, a team will be sent to Manus Island to collect documents from about 600 men still detained there.
Other refugees now resettled in the United States and those deported to their countries of origin are also entitled to claim, Dr Lomai said.