A young driver who crashed into a tree, killing his 19-year-old girlfriend, was potentially high on nitrous oxide "nangs" and could have veered off the road deliberately.
Minunyurra Wanita Lavinia Brown-West was a passenger in Blair Thomas Bailey's Holden Cruze when it left the Tasman Highway in Hobart about 7.40am on March 25, 2020.
She was rushed to hospital but died several weeks later, while Mr Bailey, then 21, was seriously injured.
In findings published on Friday, Coroner Simon Cooper said alcohol had not played a part in the crash but it was less easy to rule out other substances.
No drugs were detected in Mr Bailey's blood but there was "clear evidence" from his mother he was under the effect of a substance prior to driving.
Mr Cooper said Mr Bailey was a known regular user of nitrous oxide "nangs" to become intoxicated.
Mr Cooper said the gas, typically inhaled by discharging nitrous gas cartridges, was known to produce a rapid rush of euphoria and a feeling of floating or excitement.
"Nitrous oxide is not a substance able to be detected in blood as a result of toxicological analysis," he said.
"I suspect Mr Bailey may well have been under the influence of nitrous oxide in the immediate lead up to the crash."
Mr Cooper also couldn't rule out the crash was a "deliberate act" by Mr Bailey.
He was driving at 122km/h in a 110km/h zone and there was no evidence he applied the brakes after leaving the highway.
Multiple witnesses saw the Holden suddenly veer to the left for no apparent reason. Several motorists stopped to help at the scene.
Mr Cooper was satisfied road or weather conditions didn't contribute to the crash.
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