The four accused were the Former Shipping Corporation of Polynesia, managing director, John Jonesse, MV Princess Ashika captain, Makahokovalu Tuputupu, the vessel's First Mate Semisi Pomale and former Director of Marine and Ports, Viliami Tu'ipulotu.
The defendants all have in common a count each of manslaughter by negligence.
Jonesse also has five counts under the Shipping Act for sending an unseaworthy ship to sea, forgery, and knowingly using a falsified document.
Similarly, Ashika Captain, Tuputupu also has five more for taking an unseaworthy ship to sea for all five voyages of the MV Princess Ashika on 3rd July, 9th July, 15th July, 23rd July and 5th of August in 2009.
Pomale, the other defendants have different extra charges relating to the ship's sinking.
The Princess Ashika sank in August 2009 just north of Tonga's capital Nuku'alofa. Seventy-four people lost their lives. No women or children survived as they were all on lower decks when the boat sank.
Evidence at the trial showed the boat was suffering from rust and "huge holes" and that it was not seaworthy.
Many doors that were supposed to be watertight gave way during the disaster.
The Princess Ashika was never salvaged.
Defendants' Attorneys Laki Niu and Vuna Fa'otusia requested bail but Justice Shuster refused bail due to the serious nature of such crimes.
All defendants have been denied bail and will be taken into custody and the sentencing will be carried out next Monday, 4 March.
Issued by the: Ministry of Information and Communications, Nuku'alofa, 2011.