Seven people died in the crash on StateHighway 3 just outside of the Taranaki town of Waverley on June 27 last year.
The inquest heard one of the drivers involved had consumed synthetic cannabis that day, and the sole survivor - who lost her partner and two daughters - says she cannot remember the crash because she was "synnied out".
Ian Porteous, 80, his wife Rosalie, 76, his sister Ora Keene, 84, and friend Brenda Williams, 79, were travelling in one vehicle and died at the scene.
Ani Nohinohi was the sole survivor of the other car involved, and suffered extensive injuries. Her partner Jeremy Thompson, 28, her daughter Nivek Madams, 8, and eight-week-old daughter Shady Thompson died.
Nohinohi wrote a statement that support person Joy Clark read to today's inquest.
"I am very sorry about the tragic outcome for so many families and friends of all of the people who died as the result of the accident on June 27 2018.
"Because of some poor choices seven people lost their lives. I am so sorry for all who are suffering.
"I am grateful to the many people who worked so hard to save my life.
"I live not just with physical pain and a brain injury but also with the loss of my beautiful girls Nivek and Shady. I have wanted to join them in Heaven many times but I cannot put my family and friends through more pain.
"Again, I am very sorry about what has happened. I think about everyone who died and of my own losses and everyone who is now sad."
Innocent victims' son to fight for drugged driver testing
The son of two elderly people killed in a horror two-car crash caused by a driver high on synthetic drugs says his family will "fight" for better testing of drugged drivers.
The officer in charge of the incident, Detective Karl Reyland, said Thompson had smoked more than three cones of synthetic cannabis on the morning of the fatal crash.
He also smoked more when their car stopped at a McDonald's before the crash.
The car he was driving crossed the centre line and caused the crash, the inquest was told.
Jeremy Thompson had repeatedly consumed synthetic cannabis the day he caused the crash that killed him and six others.
Outside court Logan Porteous, son of Ian and Rosalie Porteous, said he wanted to see more support for police to test for drug driving.
"It's not our roads causing out road toll as much as the drivers," he said.
"We will as a family fight for this in the name of the innocent people who were killed in this accident, as a result of a driver under the influence of drugs."
The detective said Thompson was on his learner's licence and had more than 100 demerit points to his name.
Reyland said the vehicle stopped in Hawera and Thompson smoked more synthetic cannabis before ordering McDonald's. The inquest heard Thompson was slurring his words and making "inexplicable" changes to his food order.
He said shortly after while heading south on State Highway 3, Thompson had lost control of the vehicle, crossed the centreline and collided with the other vehicle involved in the crash.
An autopsy revealed the presence of the drugs Ketamine, Fentanyl and Rocuronium in Thompson's blood.
Reylands said it was likely that all of these drugs were administered to Thompson by medical personnel, but that Tetrahydrocannabinol (THC) was also detected in the urine.
Nohinohi limped to the witness box to give her statement, which was read out by a police officer.
Questioned, by Logan Porteous, son of Ian and Rosalie, Nohinohi confirmed that she knew Thompson had consumed synthetic cannabis before driving - but she was "wasted" herself.
When Porteous asked if she realised the impact the fatal crash had on the families involved she broke down.
Nohinohi told the coroner that she thought her partner was OK to drive because he had smoked synthetic cannabis before and then driven.
The McDonald's worker was not in court to give her statement so it was read out by Senior Constable Mark Stoud.
Stoud said the witness had observed the car smelt of cannabis and that she saw Nohinohi putting a material into a pipe and smoking it.
