The WA Supreme Court heard on Wednesday that a toxicology report showed Shaun Southern had drugs in his system when he allegedly steered on the wrong side of the Bussell Highway killing Geographe resident Jenni Pratt.
Southern is facing a charge of murder and seriously injuring passenger Karen Williams by deliberately crashing his car into their vehicle, but his lawyer said he never intended to kill anyone.
Shaun Southern allegedly steered onto the wrong side of Bussell Highway, near Capel in February 2017.
Prosecutor Justin Whalley told the court that a toxicology report showed Southern had methylamphetamine and amphetamine in his system.
Mr Whalley said Southern had an intent to kill or cause a life-threatening injury when he drove his car at high speed towards several cars before finally striking Ms Pratt's vehicle.
"We will never know when he formed the intention," Mr Whalley said.
Both cars had been driving close to the 110 kilometres per hour speed limit before the collision, the court heard.
At the point of impact, Ms Pratt had hit the brakes and was travelling at 38 km/h, while Southern was driving at 86 km/h.
Southern was flung out of his car through the windscreen and was unconscious for some time.
His car also caught fire, the court heard.
Mr Whalley said there were several near misses before the fatal crash, with other cars forced to scatter and take evasive action to avoid a collision as Southern took aim at oncoming traffic.
Two people in one car used a GoPro and an iPhone to record Southern's erratic driving.
Defence counsel Justine Fisher agreed intention was the central issue in the case but said Southern did not have an intention to kill.
She said the jury could find him guilty of the lesser charges of manslaughter and causing grievous bodily harm.
"You're going to have an emotional response," she told the jury.
"Ms Pratt was an innocent member of the community going about her business.
"All the defence is asking of you is that you reserve your judgment until you've heard all of the evidence."
Ms Fisher said Southern did not recall what happened, had some ongoing memory problems and was wheelchair-bound for some time after the crash.
The trial continues.
Australian Associated Press
