People in South Kerry are going to be asked if they would be willing to give a DNA sample as part of the Baby John case.
Officers believe the answers to what happened to the baby lies in Cahirsiveen and the Iveragh Peninsula.
Baby John was just a few days old when he was found stabbed to death on a beach in Co Kerry in 1984.
It has been just two days since gardaí confirmed they are re-opening the case.
They also conclusively confirmed what everyone already knew - that Joanne Hayes was not the baby's mother.
The then 25-year-old was wrongfully arrested and then put through a tribunal of inquiry where her personal life was thrown into the spotlight.
Journalist Joe Joyce, who was one of the first people to report on the Kerry Babies story, says many questions still remain.
He said: "I mean 34 years later we are still waiting for the answers to the same question we asked in the original article.
"How come this family, while in Garda custody, confessed to a crime they did not commit?"
The Government and gardaí have both apologised to Ms Hayes for what she went through.
While this miscarriage of justice was going on, the case of Baby John remains unsolved.
He was just a few days old when he was stabbed to death and left on a beach in Cahirsiveen.
The cold case garda unit believes the answers to what happened to the baby lies in South Kerry.
Some locals may now be asked if they would be willing to submit to a DNA test to compare it with the one they now have of Baby John.
Local journalist Anne Lucey said: "There is a lot of confustion about DNA and some people I know in South Kerry are wondering will they get a knock on the door, and are Gardaí going to be coming around collecting DNA door-to-door?
"I don't think that's going to happen. The way they will get it is if somebody comes into the frame, they may be asked.
"Or another way is if people come forward and want to be eliminated, so they will offer to give a DNA sample."
The Garda Serious Review Team and local gardaí are working together on this case.
They have moved to assure the public this investigation will be thorough, professional and sensitive.