A judge has reserved his decision on penalties in relation to whether New Zealand's second-biggest oil spill was the result of momentary distraction or a reckless disregard for environmental risk.
New Plymouth District Court heard sentencing submissions on Wednesday regarding the spilling of up to 33,000 litres of crude oil from the Tui field, which washed up along 13 kilometres of the Taranaki coast in October.
Maritime New Zealand says the field's operators knew the risks of pumping waste water into the sea from tanks not designed for that purpose, but did so to save money.
Tui's shareholding operator, Australian Worldwide Exploration, says it did ot know of any risks and the tanks were suitably designed and built.
Prosafe, which runs offshore production, says human error caused the spill when a distracted operator failed to shut off a valve.
