Pamela Stephens "trusted and believed" every word that Shane Claude Roberts said when he offered to care for her twin babies, a jury has been told.
Now Roberts, 61, is standing trial for the murder of one of the boys.
He has pleaded not guilty to the murder of 10-month-old Karlos Stephens some time between November 29 and 30, 2014. His trial began today in the High Court at Rotorua.
Baby Karlos died from "significant" head trauma that caused bleeding to the surface of his brain and behind his eyes.
The Crown argues Roberts assaulted the baby causing the fatal injuries and was "reckless" as to whether he died or not, but Roberts' lawyer asked the jury to question whether it was "truly a case of murder" or if Roberts was even the person responsible.
Karlos's mother Pamela Stephens took the stand today and gave a tearful testimony.
She told the jury she had seen Roberts as a friend and "genuinely believed" he would be "very helpful" with her twin boys.
Stephens had given birth to the "healthy" boys, Karlos and his brotherh, in January 2014. The father was not around but she was living with her mother and four other sons at the time, she said.
When the boys were about 4-months-old, she began suffering from what she said her doctor thought may be post-natal depression.
She noticed herself feeling "unwell", "depressed" and "losing interest" within herself, she said. Her doctor would not give her medication but instead suggested she go to therapy.
It was around this time, May 2014, she met Roberts through a friend. She discussed the issues and difficulties she was having in her life with him.
She said Roberts offered to care for the twin boys with the help of his ex-wife Rachael Broughton when the boys were around 4-months-old.
She said she "trusted and believed every word that he said".
Roberts, Stephens and the twin boys had been to Broughton's house in Homedale St to discuss "arrangements" for looking after the boys while she "sorted" herself out and found a stable place to live.
Stephens said it was her understanding Broughton and Roberts would take the twin boys temporarily while she took some time to "get back on my feet".
"I needed a rest and I also needed a break. I had my hands full pretty much. I needed an extra helping hand."
Stephens found emergency accommodation with her other sons but chose to leave the twin boys in the care of Roberts.
He was "wanting to be their adoptive father", she said, and she was happy for him to become that as she believed he was "capable" of doing what he said.
She decided that it would be best if Roberts and Broughton took the boys on long-term, she said, but she was still able to see the boys on a weekly basis.
Both the boys had been in good health and Stephens said she had never had any concerns for their wellbeing prior to Karlos' death.
Stephens had gone to stay at Roberts' Alison St address the week of Karlos' murder to spend time with her boys.
She stayed two nights at the house, that was without power, waiting for Roberts. She had "no money or assets" on her at the time, she said.
Roberts turned up on November 29 with the boys but only stayed at the property for about half an hour as he needed to see someone to "take care of something", she said.
He left the boys with Stephens for a time, who recalled Karlos being "feverish", "grizzly", "clingy and tired" and "just wanted to be cuddled".
Stephens told the court Roberts told her that Karlos had not wanted to drink or eat anything and he suspected he may have the flu.
She said she questioned Roberts about the boys' doctors visits and the fact that there was no power at the house.
She was concerned that her baby may have been suffering from dehydration and she wanted him to be looked at by health professionals straight away.
Roberts returned then left with the boys saying he would sort out some finances and take the boys to Lakes Care and be back later on that night, Stephens told the court.
While he was gone, Stephens said she did some things around the Alison St house to make it more "liveable".
She waited until about midnight but Roberts did not return, she said.
It wasn't until the next morning she would see him, when he banged on the door around 7.30am saying Karlos was not breathing, the Crown said.
Stephens will take the witness stand again tomorrow morning.
The trial continues.