His body was found at Kersbrook in the Adelaide Hills two days later with signs he had been bashed and stabbed to death.
A 26-year-old from Moonta, a 29-year-old from Northfield, and a 31-year-old from Ingle Farm have been arrested and charged with murder.
A 28-year-old woman from Ingle Farm has been charged with assisting the alleged offenders.
Police said the alleged murder was the result of a very minor matter but would not disclose what they believed the motive was.
Detective Superintendent Des Bray said they had a breakthrough in the case after receiving fresh information from the public.
“We did receive additional information following public appeals,” he said.
“We did received information from people within the criminal community.
“Those things combined to give us a very good understanding of what happened.”
Superintendent Bray said Mr Doelz’s family had been informed of the arrests.
“Despite an exhaustive investigation and the best efforts of investigators over several years there were no positive leads and it looked like the case may remain unsolved.”
Knives yet to be located
Police said investigators were yet to locate two knives they believed were used to kill Mr Doelz.
One of the knives had a carved wooden handle and sheath.
Police said Mr Doelz’s wallet and mobile phone have never been found.
All four accused are due to appear in the Adelaide Magistrates Court on Monday.
Police still believe a car buried under a shed in outback South Australia would provide some evidence in the case.
In July they said Mr Doelz was abducted in black Ford Falcon XR6 sedan, which was later put in a shipping container and taken to Innamincka and buried.
“Because of the massive costs involved, we’ll have some discussions with the DPP [Director of Public Prosecutions] later about the evidentiary value of recovering the car,” Superintendent Bray said.
“We’ll make that decision later because we do know that the car will provide little evidence.”