A forensic expert has told a Brisbane committal hearing that scratch marks on accused murderer Gerard Baden-Clay's face could have been made by his wife before she died.

Baden-Clay has pleaded not guilty to murdering his wife Allison and interfering with her corpse.

Her body was found at Kholo Creek in April last year.

The crown says Baden-Clay wanted out of his marriage to be with his mistress and was also motivated by the chance to clear his debts as a result of his wife's insurance payouts.

Senior Queensland Health forensic doctor Robert Hoskins examined photos of the accused taken in the hours after he reported his wife missing.

Dr Hoskins told Brisbane's Magistrates Court today that Baden-Clay's claims the marks on his face were caused by shaving were "extremely implausible".

He said it was possible some of the injuries had been caused by Allison Baden-Clay scratching her husband before her death.

However, defence lawyers argued Dr Hoskins had not physically examined the accused and suggested his medical opinion was based on hearsay.