The coroner says it is unusual and regrettable that a man did not appear at the inquest into his girlfriend's death - and another inquiry is necessary.
Libby McKay, who was 27, was driving home from a party with her boyfriend Mike Brown in Christchurch in June 2013 when she fell out of the ute, sustaining serious head injuries.
The couple attended a party in West Melton, where Ms McKay drank whisky and vodka and smoked cannabis.
After she fell out of the vehicle, Mr Brown picked her up off the road, drove to their home in Hornby and then called an ambulance. She died five days later in Christchurch Hospital.
An inquest has found police had insufficient evidence to consider prosecuting Mr Brown or anyone else.
Mr Brown was issued with a witness summons to attend the inquest, but travelled to Australia.
He wrote a letter saying he was unable to attend due to his feelings of distress over the death of Ms McKay.
Coroner David Crerar said it was regrettable Mr Brown did not attend the inquest.
"The vast majority of inquest witnesses attend a hearing to give answers to questions, and to give closure to the family of the victim."
He said another inquiry into Ms McKay's death was needed as new facts had been discovered and there were unanswered questions for Mr Brown.