Police evidence questioned in convicted murderer’s sentence appeal

The actions of WA Police investigators have come into question, as a convicted murderer's historic appeal began in the state's highest court.

Scott Austic is serving a life sentence for the 2007 murder of his 35-year-old pregnant lover Stacey Thorne, who was stabbed 21 times in her Boddington home, south-east of Perth.

The former mechanic has always maintained his innocence.

His lawyers are fighting to have the conviction thrown out, claiming key pieces of evidence may have been planted.

Among them, a packet of Winfield Blue cigarettes, allegedly stained with the victim's blood, which was photographed at Mr Austic's house.

Nowhere to be seen in the initial forensic search, it suddenly appeared in photos taken by police 30 hours later. Police now claim it was "innocently" placed on the table for the purpose of taking a photo. Questions have also been raised about the alleged murder weapon, found by police in a paddock days after SES volunteers scoured the area.

Lawyers argue the weapon would have been discovered in the initial search, if it were there.

The court is also expected to hear from forensic experts, who say the bloodied knife could not have caused the wounds on Ms Thorne's body.

After exhausting all his appeals, Mr Austic was granted a rare second chance to clear his name by the WA Attorney-General, due to concerns about some evidence.

His mother Robyn Austic said she hopes to finally have her son home.

"I believed him from day one," she said.

The hearing has been set down for seven days.