"It's a kick in the guts," he said.
"I'd just been through all that, she just got that real light sentence and it was like, you've got to be kidding me."
She pleaded guilty to two counts of ill-treating a child and one of theft in March but emails obtained by the Otago Daily Times show she repeatedly breached her bail, after charges were laid in 2019, to try to convince her ex-partner she was innocent.
"I'm going to prove to you ... that I didn't hurt our son, even if it does take a year or more," the defendant said in March last year.
"I can't believe you would walk away from me in my darkest hours and completely turn your back on us and our love.
"I won't have [my son] grow up believing I would hurt him it's not an option."
The father of the boy described the emails as "salt in the wound" and said he had continued to ignore them.
He received another the next day.
"The police accuse me of poisoning our son while he lay on life support with one on one nursing and you believe them ... I must be magical to be able to do that," she wrote.
"Worst of all is the total disregard and disrespect you have shown me never once asking me my side or giving me that decency. You have no idea what I went through in prison you abandoned me and couldn't care less ... I maybe broken but I'm not bad I'm a good person with lots of issues that are very complex."
The boy's health was immediately compromised when he was born prematurely and the outpouring of sympathy that that provoked, his father believes, got the defendant hooked on the attention.
In August 2019, she took the child to her local medical centre, concerned for his welfare, and he was transferred to hospital.
When doctors there approved his discharge, the defendant began plotting to prolong their stay.
Court documents revealed a dizzying array of websites she perused, researching how she might poison her son, and the next day she administered eye drops and her own antidepressants.
The concoction resulted in the victim's health plummeting and he was later airlifted to Starship Hospital.
In between repeating the poisonings, the woman took to social media to post photos of the unconscious boy, numerous tubes protruding from his body.
"Please pray," the defendant begged her friends.
A couple of days later she initiated a fundraiser online which yielded more than $2000, telling followers "something unknown has attacked his nervous system".
Shortly before toxicology results put the defendant in the frame and doctors discovered the shocking crimes, the woman wrote a new post.
"The best thing about the worst time of your life is that you get to see the true colours of everyone."
The victim's father remained stunned by the hypocrisy.
While the sentencing was now over, the issue of permanent name suppression was yet to be decided by the court.
He vowed to fight for the woman's name to be revealed.
"She's changed all our lives forever," he said.
"It's such a hard pill to swallow."
