Inside the Serious Crash Unit: What happens after a serious or fatal crash

Monday, 15 June 2026

When a fatal crash closes a highway and leaves motorists waiting for hours, most people only see the aftermath.

What they don't see is the painstaking work that begins once the emergency response is over – the work of specialist investigators tasked with answering one crucial question: what happened?

For Constable Graham Mako, a member of the Waikato Serious Crash Unit, that process has become a normal part of life.

The 47-year-old has spent years examining some of the country's most serious road crashes, first with the Counties Manukau Serious Crash Unit and now in Waikato after moving to Hamilton in 2023.

Before joining police, Mako worked as a fabrication engineer. Looking for a career where he could 'add value to people' and 'pay it forward', he graduated from Police College in 2009.

Since then, he has attended so many crashes that he struggles to put a number on them.

'I was literally just trying to look the other morning, of past crashes, that's totally for something else, and I'm just surprised by what I've been to.'

He's tried counting over the years, but eventually gave up.

The Waikato Serious Crash Unit attends about 100 crashes a year, on top of helping with crime scene work. Their investigations extend beyond roads and highways.

'It could be off-road crashes to do on farms, workplaces. We've had to deal with, on a small degree, gliders. Just not necessarily analysing those crashes but just going to help and collecting the evidence part of it.'

The scenes they attend can be confronting, but Mako is wary of describing himself as desensitised.

'I think to say desensitised makes it sound like, you should be bothered by it. I don't think we're bothered by it because we do this kind of work day in and day out, whether it's in crash or just on frontline work.'

The unit is automatically called to fatal crashes and incidents involving life-threatening injuries. They may also attend high-profile crashes, incidents involving fleeing drivers, or anything where police involvement means an independent examination is needed.

Once they arrive, investigators receive a briefing from officers at the scene. But Mako says experience has taught him not to take anything at face value.

'I can't count how many times I've turned up and someone's given you a briefing, told you what's happened, and then you look at it and you kind of go, oh, that doesn't make sense.

'You start following all your evidence like breadcrumbs and then you kind of go, this is the only way it could have happened.'

That evidence can be found in the smallest details.

Tyre marks, gouges in the road, scratches on barriers and scattered debris all help investigators reconstruct the moments before impact.

Using specialised surveying equipment, including GPS technology and Total Station mapping devices, the team records the precise position of vehicles, road markings and surrounding features.

'Once we've got all those distances, we measure things like the friction of the road and then from there we can start calculating speeds and times, just from the physical evidence at the scene.'

Modern vehicles can reveal even more.

Depending on the damage, investigators may be able to retrieve data showing how fast a vehicle was travelling, whether the brakes were applied, how much steering input was used and how hard the accelerator was pressed.

'We can either plug straight directly into the car's diagnostic port, like a mechanic would. But if the crash is that far gone, you might have to go straight to the airbag control module, powertrain control module or strength control.'

Vehicle infotainment systems can also hold useful information, although police must first obtain a warrant before accessing that data.

The work doesn't end when the wreckage is cleared.

Investigators can spend hours at a crash scene gathering evidence, while the wider inquiry may continue for months or even years. Sometimes they return to the site long after the crash, checking visibility, road conditions or whether something as simple as a hedge obstructed a driver's view.

Mako recalls one investigation that dragged on for years as coronial inquiries repeatedly returned to questions about tyres.

'You're always lifting a stone, opening a door, and then you're always saying what if, and then you're looking at those positive and negative enquiries.'

For a job built around tragedy, satisfaction often comes from the smallest breakthroughs.

'The highlight of my day, for example, the other day was that I managed to look at some photos and discovered that there was contact damage from one car to another and it was the most exciting thing.'

Ultimately, the evidence gathered by crash investigators can help determine responsibility, inform coronial findings and, in some cases, become critical evidence in court.

For Mako, the work is also a reminder of how quickly lives can change.

'Who knows what your actions may entail onto someone else. We can talk about slowing people down, making sure you wear your seatbelts and that, but the flow-on effect of just your small actions is just unreal.'