However, a Coroner's inquest in 2012 found the main cause was driver inattention on Mr Etuale's part. The truck's steering unit had been found to be in working order. A 30m stretch of highway where Mr Etuale lost control was in poor condition, with ruts and corrugations making it hard to handle an unladen truck, but experts said it should not have caused serious problems for a careful driver.
Those contradictory findings have left the families unsure who to blame. All the courts agree on is that the victims were not at fault, but were simply "in the wrong place at the wrong time".
Mr Sanahuja said the families faced not only the pain of losing loved ones but also the fact no one had been held responsible.
They demanded a judicial sentence or resolution in accordance with New Zealand law; the right to start a lawsuit against the responsible parties, which in normal circumstances could be the trucking firm or the driver; and an official explanation from the New Zealand government.
Mr Sanahuja said his firm, Barcelona-based Sanahuja & Miranda, was also considering a lawsuit against the New Zealand government. The firm was asking only a symbolic fee for taking up the case, he said.
Even if someone had been held responsible, ACC legislation means they could not be sued. After a fatal accident, partners or dependent children, but not other family members, may be eligible for a one-off ACC survivor's grant. The tourists' families would have been eligible only for help with funeral or repatriation costs.
The Coroner's court was told the tourists' deaths had had a devastating effect on their parents. It had also placed them in financial difficulties because Mr Serra had planned to take over the family business once he returned to Spain.
Also badly injured in the crash was a two-year-old boy, a passenger in a ute hit by the trailer as it swung across the highway.
Signs warning of an uneven surface and imposing a 70km/h limit were placed near the crash scene a day after the crash. The highway has since been repaired.
Linfox would not comment and Mr Etuale could not be contacted.