Counties Manukau Police Constable Kali Fungavaka had travelled to Tonga last August to attend his grandfather's funeral.
He was taken into police custody for a minor drunken incident and was allegedly beaten repeatedly, causing severe head injuries.
Mr Fungavaka's family, including his five young children, travelled from New Zealand and Australia to say goodbye before his life support was turned off five days after the attack.
Crown prosecutor Sione Sisifa told the Herald that he was feeling positive that all men would go to trial, which would be scheduled around October.
"It could go either way, but I'm hopeful and I'm positive. We argued the case well ... and hopefully it will come our way," he said.
Meanwhile, the Fungavaka family is seeking a six-figure compensation packet from the Tongan Government for Mr Fungavaka's children.