The "terribly sad" case of a drink driver who ran over and killed a drunken teenager lying asleep on a dark country road, only to have careless driving causing death charges later dropped, has prompted police to change its prosecution system to avoid upset and angst for future grieving families.

Danny Mather Hendriks, 18, had been on a stag do bus trip on April 5, 2014, when he decided to not rejoin the bus after a toilet stop and instead walk to his girlfriend's house in Rakaia, Mid Canterbury.

"Help, I'm stuck," he later texted his girlfriend as he walked alone.

Seen stumbling along the roadside verge of State Highway 1, concerned motorist Gordon Biggs stopped and picked him up.

Advertisement
Advertise with NZME.

After requesting to be dropped off at a Rakaia service station, Mr Hendriks then walked along Acton Rd where he fell asleep 700m from the Rakaia township, an inquest into his death heard today.

A woman, who over a six-hour period had three glasses of red wine at a barbecue, where she also had dinner, then went to a local pub where she had a fourth glass of wine, didn't see the prone Mr Hendriks until it was too late.

The driver, who was convicted for driving with 96mgs of alcohol per 100ml of blood and who has interim name suppression, had decided to drive her and two friends home from the pub. She "felt in control", she told the inquest in Christchurch.

As she reached 100km/h on the open country road, she says she flicked on her high beam headlights.

Her friend in the front passenger seat, then said, "What's that?"

The driver thought it was a "bag or animal" on the road.

At the last second, to the horror of her passenger, who also has interim name suppression, she saw a pair of legs.

The driver says she didn't have time to brake or swerve.

There was a "bang" when they hit Mr Hendriks, the inquest was told.

More than 200m down the road, the driver stopped.

With her passenger repeatedly screaming, "It's a body", she went back to see what she'd hit.

When the driver saw it was a person, she was "shocked and scared and not sure what to do".

They phoned emergency services. Mr Hendriks was pronounced dead at the scene.

Lawyer for Mr Hendrik's family, Simon Clay, today accused the woman of driving too fast for the conditions, adding that she shouldn't have been behind the wheel at all.

Police who attended the scene, on the unlit country road, found Mr Hendriks wearing a black jacket, black jeans, black socks, and no shoes.

More than 90 per cent of sober drivers wouldn't have seen a person standing on a dark road driving at 100km/h - and it would've been increased even further if that person was lying prone on the ground, according to senior constable John Isaac, of the police serious crash unit.

The woman pleaded guilty to driving with excess breath alcohol.

However, she pleaded not guilty to careless driving causing death.

Senior sergeant Scott Richardson, district prosecutions manager at the time, said the file was "fully reviewed" by two prosecutors who concluded the case did not meet Solicitor-General guidelines. The charge was withdrawn.

Since then, the process has been reviewed and changed to limit the upset and angst the withdrawal of charges can have for grieving families, the inquest heard.

Mr Richardson was aware of four recent fatal crashes on rural Canterbury roads involving people either standing or lying on the road.

No other cases resulted in charges for the drivers involved, but he accepted that they had all been sober.

However, it was unlikely that a sober driver would have avoided Mr Hendriks, police said.

"If she hadn't been driving, it could've been the next sober person who had driven over him and we wouldn't be having this conversation," Mr Richardson said.

"It's terribly sad for everyone involved."

After the three-hour hearing, Coroner Gordon Matenga reserved his decision.