There was no evidence New Zealander John Jonesse knew the ill-fated Tongan ferry Princess Ashika was unseaworthy, the lawyer for the former chief executive of the Shipping Company of Polynesia has told the Supreme Court in Nuku'alofa.

Defence counsel Laki Niu submitted to jurors in the Ashika trial that the Crown Prosecution had not provided any evidence to prove beyond reasonable doubt the eight counts against his client, Jonesse.

The ship sank, with the loss of 74 lives, in August 2009, and Jonesse, the ship's captain, Maka Tuputupu, the first mate, Semisi Pomale, Tonga's former director of marine, Viliami Tu'ipolutu, and the company itself collectively face 30 charges, including manslaughter.

In closing his argument yesterday, Mr Niu said that the Crown must prove that Jonesse knew the vessel was unseaworthy, "yet there was no evidence that Jonesse had known it was unseaworthy".

Jonesse is charged with eight counts of manslaughter by negligence in relation to the death of Vaefetu'u Mahe, forgery in relation to an audit document by David Shaw and knowingly dealing with the forged document.

He is also charged with five counts of sending an unseaworthy ship to sea, in that he is alleged to have known the vessel was unseaworthy yet he still sent it to sea, the Matangi Tonga website reported.

Niu said the Crown must prove Jonesse was negligent and also that he was grossly negligent.

"If Jonesse had marine experience, like if he was a captain, then he might have known it was unseaworthy," he said.

"But because he had no knowledge and had no marine experience the Crown must prove Jonesse knew very well that was the case of the vessel," said Niu.

He asked for jurors to base their decision only on evidence in court and stressed that because the defendants chose not to give evidence it did not mean they were guilty as the onus of proof was on the Crown to prove beyond reasonable doubt the charges against them.

On the forgery charge, Niu said that the Crown must prove beyond reasonable doubt two elements, that Jonesse wrote Shaw's name or signature on the document and that he intended to deceive someone and if the Crown could not prove this beyond reasonable doubt he should be acquitted.

Regarding the five counts of sending an unseaworthy ship to sea on all of the Ashika's five voyages from July 3 to August 5, 2009, Niu said that the most important element was that the Crown must prove beyond reasonable doubt that Jonesse knew that the vessel was in fact unseaworthy.

"No one can be found guilty if a person did not know that it was unseaworthy," he said.

The judge is expected to take up to two days to sum up the case, before jurors begin their deliberations later this week.

- NZPA