A helicopter pilot involved in a deadly mid-air collision was likely experiencing the effects of cocaine withdrawal, an alcohol hangover, and fatigue, according to a coroner’s inquest.

During the inquest on Wednesday, a toxicologist, who also provided evidence in the high-profile Erin Patterson murder trial, was part of a panel of experts discussing the probable impact of these factors on the tragic event.

Ashley Jenkinson, 40, was among the four individuals who lost their lives when his Sea World helicopter collided with another aircraft near the Gold Coast theme park on January 2, 2023.

While an autopsy revealed traces of cocaine in Jenkinson’s system, coroner Carol Lee was informed that the Australian Transport Safety Bureau concluded he was “unlikely to have been directly affected by the drug at the time of the accident.”

Witnesses reported seeing Jenkinson consuming multiple lines of cocaine and drinking 12 beers along with whisky during a New Year’s Eve celebration prior to the collision.

He had a lower level of cocaine metabolites than most people who crashed in vehicles, Victoria’s chief forensic toxicologist, Dimitri Gerostamoulos, testified.

“I can’t come to the conclusion that he was impaired or not. It is likely given the consumption of alcohol and cocaine within that period,” said Gerostamoulos, who gave evidence this year at Patterson’s Victorian Supreme Court murder trial.

Jenkinson tested negative for alcohol before starting work on the day of the crash and negative at a random drug test in August 2022.

He flew six passenger joy flights and had lunch with workmates before his last and fatal take-off just before 2pm, Lee heard.

Jenkinson’s lack of obvious intoxication at that time was not reassuring in itself, Queensland Health senior forensic physician Katherine Robinson testified.

“The subtle and fine signs of impairment are only detected through assessment by people looking to test for them,” she said.

Jenkinson signed a form that he was fit to fly, but might not have been aware of his own impairment, the inquest was told.

Australian Army aviation medical officer Dr Jeffrey Brock said testimony from witnesses about Jenkinson’s drug and alcohol use, opportunities for sleep and levels of workplace stress had shifted his opinion.

“To me, the likelihood of impairment during flying on the day of the accident has gone from possibility to probability,” Brock said.

But forensic pharmacologist Judith Perl testified Jenkinson’s ability to fly being significantly affected before the crash was possible, not probable.

“It would lead me to suspect whatever cocaine he used was pretty poor quality,” Perl said.

Jenkinson was killed along with British newlyweds Ronald and Diane Hughes – aged 65 and 67 – and Sydney mother Vanessa Tadros, 36, in the 2023 mid-air collision.

His aircraft collided 25 seconds after take-off with another Sea World Helicopter that was preparing to land at a waterside helipad at the theme park.

Nine passengers across both helicopters were injured.

Sea World owner Village Roadshow Theme Parks sold its joy flights operation to Sea World Helicopters in 2019.

The inquest will hear from Sea World Helicopters executives next week.