A painkiller-addled bus driver joked with passengers "this next part is going to be fun" before causing Australia's deadliest road accident in decades.
Brett Andrew Button will spend days in court hearing the devastation his crash brought to the families of 10 people killed in the accident and the dozens who were injured but survived the smash.
Forensic analysts believe Button took 400mg of the opioid Tramadol in the 24 hours before the June 2023 crash in which he lost control of his bus while driving a group of passengers home from a wedding in the NSW Hunter region.
The 59-year-old took a roundabout at dangerous speed before the bus slammed into a guard rail and toppled over, according to a statement of agreed facts.
He pleaded guilty in May to 10 counts of dangerous driving causing death, nine of dangerous driving causing grievous bodily harm and 16 of furious driving causing bodily harm.
Button agreed his driving ability was impaired by the opioid, which can cause side effects such as drowsiness, mental clouding and visual function deficiencies, according to the court documents.
But that did not stop him playing music and trying to foster a "party atmosphere" on board the bus as it returned from the wedding venue of Wandin Valley Estate to the town of Singleton.
Button said "if you liked that corner, you're going to like this one" and "oh, it's nothing" when worried passengers described him as "crazy" and told him to slow down.
Approaching the crash site - a nondescript roundabout in Greta - one passenger told his partner "he's coming in hot" and they replied "he's going too fast" before the bus rolled onto its side.
Button told police he did not brake coming to the roundabout because he was already going slow enough.
An analysis from investigators showed he was travelling at nearly 60km/h while going through the roundabout.
Shortly after the crash, Button called his area manager at bus company Linq and said, "I have had an accident, I f***ed up".
She replied, "You f***ing what? Is everyone OK?"
"No, there are fatalities," Button replied.
One of the first police officers present at the scene described it as a "war zone", while survivors recall seeing dead bodies and horrific injuries.
Button was previously stood down from another bus company when he was taking 40 of the opioids a week, but he did not declare that he was using painkillers when he started working with Linq in November 2022.
A pain specialist's report from June 2022 said he was dependent on opioids and vulnerable to addiction.
He took Tramadol for a back injury he suffered while working in the 1990s.
Despite confirmation of Button's heavy painkiller use, prosecutors withdrew manslaughter charges in exchange for his guilty pleas, angering the families of some of those killed.
As part of those pleas, he accepted his driving was dangerous because he had taken more Tramadol than the maximum amount recommended by doctors, engaged in risk-taking behaviour and drove too quickly to safely negotiate the roundabout.
Judge Roy Ellis has set aside three days in September when Button will hear as many as 35 impact statements on behalf of the victims.
His lawyers sought to have him appear via audio-visual link from Shortland Correctional Centre at Cessnock for at least the first day of the sentencing hearing.
"I think he should be here," Judge Ellis told Newcastle District Court on Thursday, ordering Button to be brought to court for the three-day hearing beginning on September 9.
The judge will deliver the sentence at a later date.
