It is understood the toddler suffered severe burns and deformities which even senior police and medical experts have found disturbing.
The burns extended to the boy's mid-wrists and he will need extensive skin graft surgery for the wounds.
Wellington district child protection team manager Detective Senior Sergeant Neil Holden said he had seen photos of the injuries, which would have been "extremely painful". Asked how the case compared to other child abuse investigations, Mr Holden said it was very sad and at the high end in terms of implications for the boy.
"Many of the people we deal with have injuries that are not apparent and don't necessarily come out straight away. This is one that's right in your face. It's hard to deal with, hard to process. It's right up there."
Police were seeking further advice from medical experts as part of their investigation and would speak to "other witnesses" about how the boy suffered the burns.
The abuse is alleged to have occurred at the family's Porirua East home. The mother denies inflicting the injuries and told police in a statement the boy's wounds were accidental.
Both the boy and his three-month-old baby sibling have been removed from the mother's custody and placed into Child Youth and Family care.
She was arrested on September 6 but is free on bail. Judge Geoffrey Ellis granted the woman interim name suppression this morning and remanded her till December 6.
Her lawyer, Greg Gimblett, declined to comment on behalf of his client or say whether she would defend the charges.
Asked about allegations the mother had immersed her son's hands in boiling water then failed to take him to a doctor, Mr Gimblett said: "I understand that is the basis of the police allegations. [But] as I say, I haven't seen the police case and I'm not authorised to speak to you in any way, shape or form."
A spokesman for Social Development Minister Paula Bennett said she could not comment while the case was before the courts.
Mr Holden said the toddler's plight had touched the heartstrings of a Hutt Valley woman who made quilts for child abuse victims in the Wellington area.
"This little boy has had a special quilt made for him and he'll be given that by the [officer in charge] of the case in the next little while. It's not that great to recognise that this was given to him by police after his mother [allegedly] wounded him, but if it's a small thing we can do, we'll do it."
Mr Holden said the child protection team dealt with between 350 to 400 child abuse investigations a year from around the Greater Wellington area and made about 85 annual arrests.
