Akiir Muo was expected to be grilled when the inquest resumed on Monday, but attempts by authorities to contact her have so far been unsuccessful.

Ms Muo has claimed she told police on the morning of the January 20, 2017 attack that Gargasoulas was heading to the city to run people over.

About two hours later, he mowed down pedestrians in the CBD, killing six and injuring 27.

But her claim has been rejected by police, who arrested her near the West Gate Bridge after she was pushed by Gargasoulas from his stolen car.

Meanwhile, on Monday, a detective who nominated himself to take over as incident controller during attempts to capture Gargasoulas defended his actions.

Detective Sergeant Adam Vohmann was tasked to be out on the road, ready to help in a possible arrest as Gargasoulas had led police on a pursuit after stabbing his brother on the fatal morning.

Multiple police units tailed Gargasoulas, said to be manic and psychotic, across several suburbs before his rampage.

The inquest heard fellow Detective Sergeant David Barry was incident controller that day in the effort to arrest Gargasoulas.

But when the offender entered the northwest division, the area patrol supervisor demanded to know what the arrest plan was and who was in charge.

Det Sgt Vohmann told the inquest on Monday that Det Sgt Barry asked him to phone the supervisor, Senior Sergeant Scott Poynder, and explain the plan.

"That's when I decided to take over," Det Sgt Vohmann said.

"I guess it was to try to take over the situation, and to try and appease Poynder as to who was running it."

The detective could not recall if Det Sgt Barry asked him to take over as incident controller.

When asked whether changing their roles caused any issue, he replied: "No, I had a clear picture of what was going on. The people involved understood."

Gargasoulas, who has paranoid schizophrenia, was jailed in February last year for at least 46 years.

The inquest continues on Tuesday.

Australian Associated Press