The WA Coroner's Court is probing the death of Raymond Kehlet, 47, who was found about 1.8km from his campsite near Sandstone, and the suspected death of his missing wife Jennie, 49, in March 2015.

The couple's friend and colleague Graham Milne was a suspect in their deaths but has never been charged, the inquest has heard.

Forensic pathologist Judith McCreath conducted the post-mortem examination on Mr Kehlet and said his body was in an advanced state of decomposition.

"Even following the examination, I wasn't able to come to a conclusion as to a definitive cause of death," she testified on Friday.

But Dr McCreath said Mr Kehlet had suffered bone injuries including fractures to his cheekbone, eye socket and neck.

Bones on the tips of three of his fingers on his right hand were also missing, she said.

Mr Milne testified earlier this week and said the last time he saw the couple they were chasing after their dog.

He said he did not deliberately mislead police during the search and maintained he did not know what happened to the couple.

Coroner Ros Fogliani has invited family members of the Kehlets, who have attended court every day, to provide her with letters, statements or oral testimony if they wish.

Mr Kehlet's brother has already indicated he wants to provide a message to the coroner.

Ms Fogliani also thanked the family for their assistance during the inquest so far.

The inquest has been adjourned until February 11 when evidence will be heard from forensic anthropologist Alanah Buck and hand surgeon Jeff Ecker.

Australian Associated Press