A driver who killed his brother and a young couple when he crashed into a tree after an aborted police chase in Cockburn is already in jail but now a coroner is investigating the actions of the officers.

Amy-Lee Armstrong, 25, Kyrone Eades, 24, and Ashley De Agrela, 19, died in December 2015.

Matthew Conduit had been smoking methylamphetmine and drinking when he got behind the wheel, the West Australian Coroners Court heard on Wednesday.

Conduit's brother, Mr DeAgrela, sat in the front seat with his seatbelt on, while the young couple sat in the back unrestrained.

Counsel assisting the coroner Fleur Allen said two officers in a marked police vehicle spotted the car speeding and activated their emergency lights but Conduit sped away.

She said the chase lasted about two minutes, during which Conduit drove through a red light.

The police vehicle reached 140km/hr but Conduit continued to gain distance and swerved to the wrong side of the road, prompting the officers to abort their chase.

Camera Icon Kyrone Eades and his girlfriend of 11 years Amy Lee Armstrong. Credit: GoFundMe

Conduit soon lost control and struck a tree with such force it split in two, Ms Allen said.

Mr Eades and Ms Armstrong were thrown from the car and died at the scene, while Mr De Agrela died two days later in Royal Perth Hospital.

Conduit suffered minor injuries and was sentenced in 2017 to 12-and-a-half years in prison.

The inquest heard police internal affairs conducted an investigation and did not identify any breaches of the emergency driving policy or code of conduct.

But Coroner Barry King is required to conduct his own probe into whether police actions "caused or contributed" to the crash.