Detectives are waiting for the results of DNA and fingerprint tests on a knife found at the apartment in Kimmage, which will direct the course of their homicide investigation.
The boy’s mother, aged 42, was also found with serious knife injuries at the apartment in the Riverside complex on Poddle Park.
Detectives are waiting to get the all-clear from doctors to speak to her to piece together what happened, but it is not yet clear when that will happen.
She has undergone surgery and is thought to be out of medical danger, but is under the care of therapeutic staff at St James’s Hospital.
She is a medical doctor and is thought to be from Iran. Her son was born in Ireland and she is separated from the boy’s father.
It is understood that she rang 999 before 7pm on Monday seeking medical help.
When the Dublin Fire Brigade arrived, they were unable to gain entry and sought the help of gardaí; a forced entry was achieved.
The boy was discovered in the bedroom with what was thought to be multiple knife wounds, while the mother was also found with injuries.
The child was pronounced dead at the scene.
His remains lay there until his body was removed for a full autopsy shortly before 12pm yesterday.
Gardaí are investigating indications that the knife injuries suffered may have been hours old by the time he was pronounced dead.
As part of this, they have pushed back their appeal to the public to 5pm on Sunday.
“Gardaí are appealing for anyone who was in the area of Poddle Park between 5pm on Sunday, July 9, and 7pm on Monday, July 10, to contact them at Crumlin Garda Station on 01 6666200,” said a spokesman.
The Garda Technical Bureau arrived early yesterday and began a detailed examination of the apartment and hallway.
They took various samples and will try and determine how many people had been present in the apartment, including if anyone apart from the mother and son had been there.
They also conducted an external examination of the complex and took photographic evidence.
There is comprehensive CCTV coverage at the small complex and gardaí will begin examining the footage since 5pm on Sunday.
Gardaí managed to make contact with the boy’s father on Monday night.
Locals said that the couple had separated a few years ago and that the woman lived in the apartment with her son.
It is understood that gardaí are not currently looking for anyone else in relation to their inquiries and believe they know the outline of what happened.
A local who knows the woman said she had lived in the apartment before she had got pregnant and might have been there for five years.
“She’s a doctor and she just said I’m very busy being a doctor, but she talked more about the child,” Lorraine Leon told RTÉ radio.
“She said she trained here and settled very well.
“She was telling me: ‘We wanted him for a long time, we planned him.’
“It’s very sad. Really and truly she was mad about him, ‘he does this and does that, now he’s sitting up’. Everything was about him.”