Inducing a woman to indulge in sexual acts with him on the pretext he'd die from toxic poisoning if she didn't has cost a Rotorua man is liberty for more than three years.

The 24-year-old, who can't be named for legal reasons, was sentenced in the Rotorua District Court today by Judge Maree MacKenzie to three years two months in prison on one charge of sexual connection induced by a threat and another of assaulting the same woman, his former partner.

She told the defendant he had only himself to blame that he could no longer see his child from his relationship with his victim.

The summary of facts outlined how, hiding behind a pseudonym, the man had emailed his former partner claiming he'd been beaten up and forced to drink a vile of toxin.

Because there was no known antidote, the only way he was able to purge himself was by sweating it out within 48 hours. To do this he had to have oral sex four times and three rounds of intercourse with the woman.

The email also claimed pictures of her semi-naked body would be posted on the internet and three people she loved, her son included, would receive bullets if she didn't give in to the emailer's demands.

The woman suggested he go for a run to sweat out the toxin, which he rejected. He emailed her again saying she would get a car if she followed his instructions.

Believing his life was in danger and because she didn't want their child to grow up fatherless she gave in to his demands.

According to the summary, further threatening emails were sent promising the woman large sums of money but none eventuated.

After yet another email in January 2016 the woman began to suspect it was her former partner sending them.

When she confronted him he denied knowing about them or photos she showed him, telling her he'd make sure she never saw their son again.

When she attempted to push him away he knocked her to the ground.

Crown prosecutor Ngaroma Tahana said the man had showed no remorse, however lawyer Harry Edward argued the complete reverse was the case.

Describing the matter as "bizarre" Edward said the man had suffered considerable emotional upset and was in a new relationship with his partner.

"In terms of true criminality it is highly unlikely he will appear in court again on any matter," Edward claimed.

The man's current partner, who was in the public gallery, wept when the sentence was imposed.

The defendant pleaded guilty to both charges after receiving a sentence indication only days before his trial by jury was to begin in March.