A Chinese fishing company accused of marine pollution in French Polynesia says its fishing boat discharged hundreds of litres of liquids, including fuel, for safety reasons.
The boat, the Xin Shi Ji 203, was intercepted off Tahiti last May after airline pilots spotted a slick emanating from it.
Its lawyer told the criminal court in Tahiti that a burst pipe onboard risked immobilising the engine so the crew pumped the liquid into the sea.
She told local television after the trial that the crew acted in an emergency to save the ship, which carried 100 tonnes of fuel.
Authorities say the captain never signalled any problems and showed no sign of planning to return to port.
The court is expected to give its verdict on 28 January.
It will also rule on a demand by the defence that the trial should have been held in China.
The defence said France failed in its obligation to notify China of the incident.