Coroner says driver may have been on laughing gas when passenger killed in crash

Coroner Simon Cooper also found that he could not rule out that Blair Thomas Bailey of Acton Park deliberately crashed off the Tasman Highway into the tree at Mornington on March 25.

Mr Cooper's findings came after an investigation into the death of nineteen-year-old Mininyurra Wanita Lavinya Brown-West, who died of head injuries and blunt trauma of the chest, pelvis and right leg.

In his findings, Mr Cooper said that Bailey was a known regular user of nitrous oxide.

"The gas, when inhaled typically by discharging from nitrous gas cartridges, is known to produce a rapid rush of euphoria and a feeling of floating or excitement for a period of time," he said.

Mr Cooper said that there was clear evidence from Bailey's mother that he was under the effect of a substance before driving.

He said nitrous oxide, commonly known as laughing gas, was not able to be detected in the blood in toxicological analysis.

"I suspect that Bailey may well have been under the influence of nitrous oxide in the immediate lead-up to the crash," he said.

Mr Cooper said that witnesses saw the Holden Cruze suddenly veer to the left for no apparent reason.

"I am quite satisfied that Bailey was driving at an excessive speed of about 122 km in a 110 km zone," he said.

"There is no evidence that Bailey applied his brakes after leaving the highway nor that there were any steering inputs indicating an attempt to collide with the tree.

"I cannot exclude as a reasonable hypothesis that the crash which killed Ms Brown-West was the result of a deliberate act on Bailey's part."

Mr Cooper said that dash camera footage from a school bus showed that Bailey did not indicate to leave the highway.

He said Bailey was charged by the Director of Public Prosecutions (DPP) with causing Ms Brown-West's death by negligent driving.

However, the DPP later withdrew that charge, apparently having concluded that Bailey's successful prosecution was unlikely.

"It is not part of a coroner's role to comment on the decision to prosecute or discontinue a prosecution once it has commenced, whatever the coroner thinks of that decision," he said.

Bailey was seriously injured in the crash and remained in hospital for a lengthy period.