About 400 people with criminal histories are being targeted in an upgraded police investigation into a cold case murder in South Australia.
Police have established a new task force in a bid to solve the disappearance and suspected murder of Susan Gae Goodwin in Port Lincoln in 2002.
Letters are being distributed to prison inmates in Port Lincoln and anyone under the supervision of corrections officers, in order to seek information about the death of the 39-year-old.
Detective Superintendent Des Bray said over the past year a number of prisoners had been in touch with major crime with information about a range of cold cases.
"Correctional Services have been very supportive of our cold case strategy and this prison strategy is really important to us," he said.
"On Wednesday evening every prisoner in Port Lincoln had a letter put under the door of their cell asking that they potentially help themselves by helping us.
Police said prison inmates were reminded of the potential both for immunity from prosecution for anyone involved on the fringe of a crime or sentence reductions.
Supt Bray said the disappearance of Ms Goodwin had been subject to a full case review that led to several new lines of inquiry.
"Our experienced investigators believe the answer to this case lies in the local community," he said.
"We believe that she was murdered and that her body has been disposed of within a 30-kilometre radius of this town."