WA woman's road death remains a mystery

The mysterious death of a mother of two found lying on a Perth road with head injuries is unlikely to ever be solved after potentially important CCTV footage was inadvertently erased, a coroner has found.

Ms Hansen, whose first name is not used for cultural reasons, was found by a passer-by and died at Fiona Stanley Hospital in June 2016.

The 25-year-old may have sustained the injuries by being struck with a blunt object, hit by a glancing blow from a vehicle or falling while trying to avoid a car, Coroner Michael Jenkin said in his findings released on Wednesday.

He said it was impossible to say whether she was assaulted, and a police investigation failed to identify anyone likely to have been responsible.

Two officers viewed CCTV footage from a house shortly after Ms Hansen was found but it was inadvertently erased.

Mr Jenkin said that significantly hampered the investigation and the CCTV recorder should have been seized immediately, especially because the footage could not be downloaded.

He made an open finding into Ms Hansen's manner of death.

"This is obviously a very unsatisfactory state of affairs and no doubt adds to the angst and grief that the deceased's family and friends feel with respect to her tragic death," he said.

Ms Hansen had attended a gathering at a Willetton property, and at about 10pm home occupier Preston Culbong called police to disperse the group, the West Australian Coroners Court heard.

Before police arrived, Ms Hansen had a physical fight with her boyfriend Steven Pickett - who was on bail and was not supposed to be in contact with her - and he punched her to the side of the head.

Mr Pickett left when police arrived but returned later and had another fight with Ms Hansen.

At about 11.30pm, Mr Culbong drove Mr Pickett and another man to Bullcreek train station, then agreed to take Ms Hansen to the station too.

But during the drive they had an argument and Ms Hansen threatened to tell Mr Pickett she had had sex with Mr Colbung, so he stopped the car and gave her directions to walk to the station.

It was raining at about 12.15am when a driver saw Ms Hansen lying on the road, some 1.8km from where Mr Culbong said he dropped her off, and called emergency services but she could not be saved.

Mr Jenkin noted Mr Culbong had denied any involvement in Ms Hansen's death and found there was no cogent evidence to link him to it.

He also said it was possible another vehicle picked up Ms Hansen after Mr Culbong dropped her off.