Emotional Perth police recount night of horrific drug-fuelled pursuit crash that killed three

Two police officers involved in a deadly high-speed chase in Perth's south in 2015 have broken down while recounting the horrors of that night at a coronial inquest.

The V8 Holden Commodore they had been chasing through Cockburn smashed into a tree at more than 140km/h, splitting the vehicle in two.

Back seat passengers Kyrone Eades and Amy-Lee Armstrong, both 23, were flung onto the road and died instantly.

Ashley De Agrela, 19, died from his injuries two day later.

His 27-year-old brother Matthew Conduit was jailed for 12 years over the meth-fuelled crash.

Senior Constable Joel Vanson told an inquest he started chasing Conduit's car because it was speeding and ran a red light.

"As soon as he flicked his lights off and went onto the wrong side, I stopped," he said.

Moments later, the car crashed.

Mr Vanson fought back tears, describing the moment he arrived at the wreckage.

"It was terrible," he said.

His partner Darren Cramer also became emotional, telling the inquest it's a night he's "never going to forget".

Mr Eades' relatives told reporters it was "heartbreaking" to listen to the details again.

"It just brings back old memories of what's happened in our lives," his mother, Francina Wynne said.

Mr Eades' Aunt, Jennifer Loo, also said he left behind three "very sad" children.

"They haven't got parents anymore and my sister hasn't got her son, so it's very hard," she said.

An internal police investigation cleared both officers of any wrongdoing.

The Coroner will hand down his findings at a later date.