A motorcyclist was heavily medicated and nearly five times over the legal alcohol limit when he crashed his Harley-Davidson killing himself and a teenage girl riding pillion.
Dee McMahon, 49, and Natalia Austin, 18, were killed when their motorbike smashed into a median barrier in Wellington on June 28 last year after he had spent the night before drinking heavily.
Ms Austin's boyfriend's mother was the partner of Mr McMahon.
The motorbike was travelling at up to 140km/h at the time of the collision which came as Mr McMahon failed to negotiate a sweeping left-hand end just after the Terrace Tunnel on State Highway 1.
Witnesses described the bike as a "black blur" and noted that its speed was "like I was standing still. He was flying. He was going like hell".
The duo were thrown from the bike and Mr McMahon died from a combination of extensive neck and head injuries while Ms Austin died from chest injuries.
A toxicology report found Mr McMahon had taken a variety of medications, including anxiety, depression, pain relief and antipsychotic medications which should not have been mixed with alcohol.
It was also found he would have had to drink between 22 and 42 standard drinks to return a blood alcohol level of 239 milligrams per 100 millilitres of blood that was registered after the crash.