After his car was hit by a methamphetamine-affected driver, Nick McEwan sat in his wrecked vehicle unsure whether his three children in the back were alive.

He spent an excruciating half an hour trapped in his seat while emergency services rushed to the crash site on State Highway One, near Herbert.

The McEwan family of five was helicoptered to hospital on September 12 last year and all but one made a full recovery from their injuries.

McEwan's youngest son — 3 at the time — suffered a broken neck and a broken right arm, which was never likely to be fully functional again.

Their ordeal was recounted in the Dunedin District Court this week at the sentencing of 47-year-old Jotham Reuel Miller, who had pleaded guilty to driving under the influence of a drug and causing injury.

Judge Jim Large jailed him for a year and acknowledged the penalty might be of little comfort to the McEwans.

"No sentence I can impose today will in any way restore your family to the lives you had before this day.

"I wish I could do something which would allow that to occur but the reality is I can't," he said.

They had been attending a family birthday that weekend and were travelling home from Oamaru to Waitati.

Miller was heading in the opposite direction in an unregistered ute with bald rear tyres, towing a trailer.

Unknown to McEwan, the defendant had been swerving within his lane, veering over the centreline, for 5km before they collided.

"I saw him in the grass verge when I came round the corner and then he lost control and came straight across ... I gave [the steering wheel] a yank," McEwan said.

"I did all I could do and if I hadn't been on my game and concentrating, it could've been a different story."

He fractured his ribs and damaged his hips, while his wife suffered a broken rib and chipped teeth.

Their oldest child, 6, received multiple scalp lacerations and a broken finger, their 5-year-old was bruised and the youngest boy continued the recovery from his life-changing injuries.

Miller initially told police it was the wind that caused his erratic driving but a blood test revealed the real reason — methamphetamine and methadone.

Miller continued to deny the drugs had impaired his driving.

The court heard the defendant had been exposed to alcohol at 3, was first intoxicated at 10, began social drinking at 15 and was introduced to meth in Australia, which began a pattern of addiction.

Counsel Karlena Lawrence said her client had almost immediately engaged in counselling after the incident.

Miller and his victims had met at a restorative justice conference during which he apologised repeatedly.

McEwan said he believed the driver was sorry for what had happened but his remorse could only be measured by how he conducted himself in future.

He drove past the crash site every week and it had taken time to rationalise the episode.

"[We were] in the absolute wrong place at the absolute wrong time," he said.

"Unfortunately, that's life."

Miller was given leave to convert his jail term to home detention (if a viable address becomes available) and was banned from driving for two years.

He was also ordered to pay the victims $2070, though Judge Large said if he had been able to afford more, a figure in the "hundreds of thousands" would have been justifiable for what he had put the McEwans through.

- Rob Kidd, ODT