27-year-old Chen Liu, who also went by the name of Anthony Liu, was found dead in marshland surrounding the Georges River in Sydney's south last year.
Police say the severely decomposed body was found just after 6:00pm (AEDT) on 1 November 2008 by two children, aged 9 and 14, who told their parents they had seen a body in Oatley Bay while on a canoeing trip.
Police say Mr Liu had been dead for 12 days before being discovered.
The Homicide Squad has been handling the case in conjunction with the Hurstville Local Area Command, forming Strike Force Renfree, but so far no arrests have been made.
They have now released an X-ray of the 27-year-old's skull and neck, which shows it was filled with 34 nails.
"Post-mortem examination results revealed Mr Liu was shot repeatedly to the head with a high-powered nail gun. Similar types of nail guns can fire nails up to 85 millimetres long," Detective Inspector Mark Newham of the Homicide Squad said in a statement.
(Thanks to ataxi, I think.)