When Neil awoke he retrieved Isaiah from the car and testified earlier this week the baby was hot, limp and lifeless.
Te Whetu testified that she woke up about 3.30pm when Neil handed her the infant, and tried to give Isaiah a bottle in bed at the same time Neil returned to the bed.
"He just felt like any other kid felt when they're in a deep sleep," Te Whetu told the court.
Gray questioned whether Te Whetu was worried but the 29-year-old said she wasn't concerned by the baby's condition.
Te Whetu told the jury of eight men and four women that Isaiah was only in the bed with her and Neil for a few minutes.
When Isaiah wouldn't take the bottle she put him in his cot. At 6.30pm Te Whetu woke up again and went into a full panic when she couldn't rouse the baby.
Gray questioned what blankets were in the cot to which Te Whetu replied quilts and another big blanket.
Gray also asked whether Isaiah's older, preschool-aged brother had climbed into the cot but Te Whetu said he had never done that before.
The court heard that Neil had a much closer bond with his daughter than with his two sons and refused to look after the boys.
When Te Whetu discovered Isaiah lifeless in the cot she rang 111 but Neil was so sleepy he could not relay the CPR instructions to Te Whetu.
She screamed at him to "f**ken wake up" but he did not.
Gray questioned whether Isaiah might have been injured at some point that day, when a large bruise and abrasion was found on the baby's abdomen.
Te Whetu admitted she had not noticed any bruising that morning when she dressed the little boy and only noticed it when paramedics arrived that night.
"So something happened to Isaiah that afternoon," Gray asked.
Te Whetu: "I'm not sure if I just didn't see it because I wasn't looking."
Gray: "The bruising on the tummy is pretty big though isn't it?".
Gray asked whether Isaiah showed any signs of discomfort when handed to Te Whetu at 3.30pm but the young mother said he didn't.
Earlier in the day there was much debate about whether the doors, windows and sunroof of the car were open when Isaiah was left in his car seat on the 20C day.
Crown prosecutor Richard Marchant pointed out Te Whetu had contradicted the original statement she gave police, in her evidence yesterday.
Te Whetu, who is a witness for the Crown in the case, said she couldn't remember whether the car doors, other than her driver's side, were closed when she raced inside the house after returning from Kawerau where she and Parangi had bought the synthetic cannabis off a cousin.
Under questioning by Marchant, Te Whetu's answers in court yesterday were shown to be different from the statement she gave police on November 3, 2015, the day after Isaiah died.
In her police statement Te Whetu said Isaiah was seated behind her in the back seat but in court she said the baby was on the passenger side of the rear seat.
She said after reading medical notes for Isaiah, she believed he had died from hyperthermia or heatstroke and therefore the doors, windows and sunroof of the car must have been closed that day.
Te Whetu also said she assumed someone else would remove Isaiah from the car, and that her mother and sister-in-law did a lot of the parenting of her children.
Parangi's son Marcus Te Whetu told the court he called around to his parents house that afternoon to wash his new car.
He saw the car Isaiah was asleep in but didn't know his nephew was inside.
Te Whetu said he though the driver's side doors were closed.
He had called at the house earlier that morning to "check on my nephew to see if he was alright".
"I cared for him and I wanted to make sure he was alright 'cos I was working night shift."
Marcus Te Whetu found the baby on a mattress in the lounge with a full nappy and a "runny" nose.
When defence counsel Julie-Anne Kincade asked Marcus if he noticed anything on Isaiah's body when he took the baby's nappy off, he said no.
Later that day he returned to the house after 2pm and was there about 3pm when Isaiah's two older siblings were dropped off in a van from Kohanga Reo.
The driver and monitor of the van testified that Neil came outside to retrieve the two sleeping children from the van and put them on the trampoline.
They did not see Isaiah or any other adults except for Marcus. The two women did not know the family, other than to say hello to.
The court also heard from Darlene Hunt, the partner of Thompson Williams - who sold Parangi the synthetic cannabis that day - who said she had only met Lacey Te Whetu once by chance outside shops in Kawerau.
On the day she saw Parangi and Te Whetu at the shops she said Isaiah was in a car seat in Parangi's car, in the rear passenger side of the car.
The trial is set down for three weeks.
