The asylum seeker says he can identify several others involved in the death, including Australians employed at the centre, and would testify anywhere but in Papua New Guinea.

Manus Island police regional commissioner Alex N'Drasal confirmed that a number of asylum seekers were reluctant to testify, but said several would give evidence in the trial, set to run over three days before a judge in East Lorengau.

Mr Barati died during a night of violence at the centre on February 17 last year in which 69 people were injured when the centre was invaded after two days of protests, with one losing an eye, one shot in the buttocks and another having his throat slashed.

A review for the Abbott government interviewed one witness who claimed a Salvation Army employee initiated the attack, but was joined by about 10 others, including PNG locals, PNG guards and Australian employees.

Commissioner N'Drasal said police had the first names of two New Zealanders who were allegedly involved in the attack and who were now living in Australia. He said attempts to have them identified and repatriated had been frustrated by their former employer, who no longer is a contractor at the centre.