Jury retires in Tonga ferry sinking trial

Underwater view of the ferry on the sea floor. Photo / Supplied

The jury in Tonga's biggest criminal case, the Kingdom's horror boat sinking, has retired to consider its verdict.

A total of 74 people died when the ageing and deteriorated Princess Ashika went down in heavy seas north of the the capital Nuku'alofa in August 2009.

The government-owned Shipping Corporation of Polynesia, which bought the 37-year-old ferry shortly before it sank, is charged with manslaughter over the deaths, along with the company's former chief executive, New Zealander John Jonesse.

Also on trial is ferry captain Makahokovalu Tuputupu, first mate Semisi Pomale and former Ministry of Transportation director Viliami Tu'ipulotu.

Since the trial began on Valentine's Day, the jury of seven has heard from a range of witnesses, including survivors, crew and shipping specialists who added their opinions on what caused the vessel to lurch violently and sink with little warning during its overnight voyage.

No women or children managed to survive because many were sleeping on the lower decks.

Among evidence has been claims the boat was riddled with rust and "huge holes", and that it was not seaworthy. There were also question marks over whether it was correctly registered and thoroughly tested by its new owners.

According to a report by Matangi Tonga newspaper, Supreme Court Justice Robert Shuster completed his summing up on Wednesday, telling jurors they were the sole judges of the facts in the trial.

"When it comes to the facts of this case, it is your judgment alone to decide a guilty or not guilty verdict and you must only base your decision solely on evidence presented in court and not of anything else," he said.

The five defendants opted to remain silent throughout the trial, a choice that should not play a role in the jury's decision, the judge said.

"It is their right enshrined by law because the burden of proof is on the Crown to prove the charges against each defendant beyond reasonable doubt," he said.

He also directed them to consider closely the ship's construction and the condition of safety equipment and items like watertight doors, many of which gave way in the disaster.

"If it is not of a reasonable standard the law states that ship is unseaworthy," Judge Shuster said.

"The law is also clear that a ship must not proceed to sea without valid certificates including load line and safety certificates, under any circumstances."

The newspaper's editor Pesi Fonua said there was some relief among Tongans that the trial was drawing to a close, with families of the victims eagerly anticipating the result.

He told AAP that many people believed the trial had been poorly handled.

"It would be true to say that many people feel the case has been as full of holes as the boat itself," Mr Fonua said.

He said Tonga's judiciary wasn't well equipped to deal with such a big trial and that lawyers involved lacked experience needed to inspire confidence in Tongans that justice would be done.

Reports that voluntary compensation payments had been made to some families had further "complicated things", Mr Fonua said.

"A lot of people are questioning this whole process to be honest.

"They've lost a lot and they want to believe that things will change for the better after this. We really hope that that is the case."

- AAP