Bus driver Brett Button admitted to taking a large amount of painkillers and joking with passengers before causing Australia's deadliest road accident in decades.
The 59-year-old was driving a group of passengers home from a wedding in the NSW Hunter region in June 2023 when he lost control on a roundabout, causing the bus to roll onto its side.
Passengers on the bus were returning from the Wandin Valley Estate wedding venue. (Darren Pateman/AAP PHOTOS)
A court is due to sentence Button on Wednesday in Newcastle but will first hear evidence as to the appropriate punishment, including likely victim impact statements from family members of those killed.
A judge ordered that Button, who is being held in Shortland Correctional Centre at Cessnock, be brought in to appear for the hearings in person.
Button 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.
Forensic analysis suggests he took 400mg of the opioid Tramadol, which can cause side effects such as drowsiness, mental clouding and visual function deficiencies, in the 24 hours before the crash.
Button agreed his driving ability was impaired by the opioid but, according to court documents, was trying to foster a "party atmosphere" on board the bus.
He told worried passengers who had asked him to slow down, "if you liked that corner, you're going to like this one", the documents stated.
Members of the group, which was returning from the Wandin Valley Estate wedding venue to the town of Singleton, commented on Button's speed as he approached the roundabout in Greta.
One passenger told his partner "he's coming in hot", to which they replied "he's going too fast" before the bus rolled onto its side.
Brett Button was trying to foster a "party atmosphere" on board the bus, court documents said. (Mark Russell/AAP PHOTOS)
Button told police he did not brake coming to the roundabout because he was already going slow enough, with an analysis from investigators showing he was travelling at nearly 60km/h.
Prosecutors withdrew manslaughter charges in exchange for Button's 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 and drove too quickly to safely negotiate the roundabout.