A judge says company that owned the Pike River coal mine at the time of the fatal explosions in 2010 should not have been mining because it was unsafe.
In an interim decision last month, Judge Jane Farish found Pike River Coal Ltd guilty of nine charges laid by the Department of Labour.
The department investigated the series of explosions that killed 29 men at the West Coast mine in November 2010.
In her final decision released on Monday, Judge Farish said Pike River Coal Ltd failed to implement and audit its own inadequate safety plans and procedures, and that errors transpired over a number of years.
She said the company failed to take all practicable steps to ensure the safety of its workers.
In the decision the judge said the company "should have ceased mining to allow for the risk of unpredictable but foreseeable events"
Nicholas Davidson QC said those words vindicated the families in their two year battle for accountability.
"It's expressed in very cogent terms. The judge has used language which I think for the reader, particularly for families, allows them at last to make a judicial link between the breaches which have occurred and the deaths of the men."
Judge Farish found there were 13 steps the company should have taken to manage methane gas but did not, ranging from the management of diesel emissions from vehicles to the drainage of gas from the coal seam.
The judge said there was a lack of any thorough investigation on the geology of the rock where a large expansion had recently taken place.
She said that the fresh air base, where those underground retreat to in an emergency, was inadequate and required a person to climb a series of vertical ladders over 100 metres in total, or to evacuate through the main 2.3 kilometre portal tunnel.
Judge Farish said the base was excavated in coal and was not lined with incombustible products.
The company will be sentenced in Greymouth in July.
