Roy Naylor, 27, and his 19-year-old wife, Sonya, were last seen at a Glenelg motel where they were living in June 1984.
The Naylor’s were believed to be involved in the distribution of drugs in South Australia and had links to New South Wales.
After writing to family in late June or July 1984 the Naylor’s have not been seen or heard from since.
In 1990 a coroner ruled that the pair were most likely dead, probably the result of their heavy involvement in the heroin trade.
The pair reportedly owed a substantial drug debt and were known to be part of a large-scale syndicate bringing heroin to Adelaide from Sydney before distributing it to local dealers.
Roy Naylor had been jointly charged with drug trafficking but had not faced trial at the time of his disappearance.
Extensive inquiries have been conducted throughout Australia and with Interpol overseas, but there is no evidence the couple are alive.
A reward of up to $200,000 is on offer for information that leads to a conviction in this case or the recovery of the victim’s remains.