Daniel Morgan was found dead in a London pub car park in 1987.
Despite five police investigations, nobody has been convicted of his murder.
His brother Alastair Morgan has joined investigative journalist Peter Jukes to tell the story of his brother's murder in weekly episodes.
Mr Morgan told BBC Wales: "The full story has never been told in a coherent, logical way so that people can understand what really took place here.
"It's a really outrageous case. I want the public to have the chance to hear what happened," he added.
When Daniel Morgan's body was found in March 1987 he had been attacked with an axe shortly after drinking at the Golden Lion pub in Sydenham.
Police investigations continually failed to convict anyone for the crime, and the case has been riddled with accusations of corruption and cover-ups.
An independent panel has been established to examine the circumstances of Mr Morgan's death, and the persistent failure of police to convict anyone.
Mr Morgan, from Llanfrechfa, near Cwmbran, was 37 when he died.
Peter Jukes, the investigative journalist who is presenting the new podcast, said he was "astonished" to hear the details of the story once he began his research.
"We are hoping for witnesses to come forward that will jog people's memories. There's a lot of open-source material available, so people can begin to put together a story themselves, and maybe make new connections."
As part of the recording process, Alastair Morgan revisited the scene of his brother's murder with the podcast's production team.
Mr Jukes praised the podcast genre as a means of telling in-depth, complicated stories.
"A podcast is great because you're limitless in what you can do. You can move around, and you can rely on a single voice - a presenter or, in Alastair's case, the brother of a murder victim," he said.
The producers are hoping to emulate the success of the Serial podcast, which tells one true story over the course of a series. The first series raised questions about the conviction of an American man for murdering his high school girlfriend.
The Daniel Morgan Murder podcast will be released to registered subscribers before Christmas, while it will become more widely available for download in the new year.
A new crime podcast is hoping to shed light on the unsolved murder of a Welsh private investigator.