A New Zealand businessman faces a fine and time in jail if found guilty of manslaughter by negligence, over the sinking of the Tonga ferry Ashika last August.
Seventy-four people died when the vessel sank during an overnight voyage from Tonga's capital, Nuku'alofa, to an outlying island.
The former managing director of the Shipping Corporation of Polynesia, John Jonesse, a New Zealander is due in court on Monday, along with the ferry's captain and first mate.
The charge against Mr Jonesse relates to the death of a 21-year-old woman, whose body was the only Tongan corpse found following the disaster.
The three men are also accused of sending an unseaworthy vessel to to sea, and a charge of manslaughter has been brought against the Shipping Corporation itself.
Mr Jonesse is currently on bail, after being charged with forgery and knowingly dealing with forged documents.
Tonga's police have a task force of 10 officers on the case, and the investigation is continuing.
The report from a Royal Commission of Inquiry into the sinking is to be presented to Tonga's king next week. The commission heard that the badly rusted ferry was unseaworthy and not properly checked before it was bought.
Interim ferry charter
New Zealand is to help pay for an interim ferry service to connect Tonga's islands.
The Government says the interim replacement ship, the Malaysian ferry Ajang Subuh, has been independently checked by marine surveyors.
Foreign Affairs Minister Murray McCully says the survey company London Offshore Consultants found it seaworthy and fit for purpose.
New Zealand and Australia will each pay $NZ2.5 million towards the year-long charter. Tonga will cover the ferry's fuel and maintenance costs.
A permanent vessel under construction in Japan and funded by the Japanese government is due in Tonga late this year.
Supermarket owner Ofa Semiki says she will be able to reopen her shop on one of the outer islands, which she had to close because there has been no ferry to take supplies there.
