Tongan Attorney-General John Cauchi has appointed prosecutors from New Zealand to assist with prosecutions arising from the sinking of the ferry Princess Ashika.
Seventy-four people died when the rusty ferry sank in August last year.
Since a Royal Commission began investigating the tragedy, a number of people involved have been arrested and charged.
The commission found there was negligence, lack of due diligence and the ship should never have been bought.
Mr Cauchi believes Wellington Crown solicitor Grant Burston and New South Wales Deputy Senior Crown Solicitor Dan Howard will achieve a just outcome.