WARNING: This story refers to child sexual abuse. For help and crisis information, see below.

When she met Geoffrey Muir on Tinder, she never imagined that within two years he would have destroyed her family – abusing and raping her older daughter until her 12th birthday, then turning his attention to her five-year-old.

Muir was trusted with the girls. He was charming. She thought he was a good man.

But now she knows he is a monster – a cunning predator, a manipulator, a sick child sex offender.

And she worries there are more victims out there.

In early 2020, the woman met Muir, then 53, through the dating app Tinder.

The pair ended up as friends and Muir spent a lot of time at the home she shared with her young daughters.

Eventually, he had almost daily access to the girls and was trusted to be alone with them.

No one had any idea what he was subjecting the children to until 2023 when the older girl disclosed Muir’s abuse, worried he would do the same to her little sister.

It was too late.

The woman went to police in 2023 and Muir was charged with 12 counts of sexual offending against the older girl, ranging from committing indecent acts to rape and exposing her to pornography.

He was charged with two counts of sexually abusing the younger girl.

A further two charges were laid relating to Muir making or possessing objectionable material including images and video of the sisters.

Muir was arrested and charged in Tauranga, where he was living at the time.

The offending happened elsewhere in New Zealand.

At his first appearance in the Tauranga District Court, he pleaded guilty to most of the charges. At sentencing on Monday he pleaded guilty to the balance as well as several new charges.

Geoff Muir was living in Tauranga when he was arrested and charged with a raft of child sex offences. Photo / Facebook.

Muir’s litany of offending was outlined in a 12-page summary of facts, which the Herald was provided.

In November 2021, he began sexually abusing the older of the two girls, who was 10.

“During this time, [Muir] took every opportunity to sexually abuse [the girl] with increased frequency to the point where the abuse became normalised and expected – with a measured severity from genital touching and rubbing to sexual violation,” the summary said.

“To avoid detection of his offending the abuse took place in [the girl’s] bedroom at night; in her mother’s bedroom when no one else was home with windows, curtains and doors closed … and within the privacy of his truck after bribing [the girl] to travel with him as a passenger.

“The sexual abuse of [the older girl] stopped in 2021 before her 12th birthday.”

Muir then began abusing the younger girl, who was just 5 years old.

“[He] was tactful and calculated in his pursuit to sexually abuse [the little girl] and continually ensured that she would keep the abuse as their secret.

The Herald has chosen not to publish the specific details of each charge – most of which were representative, meaning there were multiple offences of the same type that could not be pinned down to a specific date.

Muir’s offending against the older girl escalated steadily, with more intrusive violations.

He gave her a sex toy and encouraged her to use it, then hide it under her pillow.

“It’s fun being naughty, isn’t it?” he said to her during one assault where he used the toy.

He began to bribe the girl to go with him to the supermarket, among other places, saying he would buy her chocolate and giving her $20 on at least one occasion.

“[Muir] employed this tactic to lure her into his truck for the sole purpose of having time and privacy to sexually abuse her,” police said.

“Typically, before or after touching [her] in her bedroom, [Muir] would give her his cell phone. He instructed and encouraged her to use his cell phone for the sole purpose of watching pornography on Pornhub.

“This occurred with such regularity [the girl] lost count of the number of times it happened.”

Police said Muir’s sole purpose of encouraging the girl to watch porn was “to sexualise her behaviour with the express intention to get her to engage in the sexual activity” she was exposed to.

Just after the girl turned 12, Muir’s abuse stopped.

Police said the only reason for that was because he had “turned his focus” to her younger sister.

“The defendant used the times when playing with [the girl] to sexually abuse her,” police said.

“While ... alone together, [Muir] would playfully let [the 5-year-old] catch him watching pornography on his cell phone as if it was a game,” police said.

“He would subsequently let her watch pornography on his cell phone. He knew this piqued her interest to the point where she asked to see more ... the watching of pornography was intertwined with the sexual abuse.”

Muir also filmed lewd videos involving the girls and took photos – mostly in their mother’s bedroom.

When Muir learned the girls’ mother was going to police he went into the Tauranga station with a lawyer and made a full confession.

“He admitted... that he let [the girls] watch pornography on his mobile phone to manipulate the situation that would lead to sexual offending,” police said.

“He found this exciting.”

Muir was sentenced by Judge Paul Geoghegan, who began proceedings by inviting the girls’ mother to read a Victim Impact Statement.

The woman said her older daughter only came forward because she feared Muir would abuse her little sister.

“Those fears were founded,” she said.

She said Muir was “sick” and “monstrous” and had “manipulated, groomed and used” her for years – all to get to her little girls.

“The wounds are not physical but they run deep and are real and personal,” she said.

“He took something so precious – my children’s innocence … their ability to grow up without trauma.

“As a mother I am broken. I failed to protect my children from a monster hiding in plain sight … I am living every parent’s worst nightmare.

“It is utterly heartbreaking ... This is a life sentence, a burden of harm we will have to navigate... I cannot take away the memories … I can only tell them that what happened is not their fault.”

Geoffrey Muir in a video taken while he was fishing. Photo / YouTube.

She said Muir was “a cunning predator” who hid behind his “charm”.

“I am firmly convinced my children are not his first victims,” she said.

“I have absolutely no doubt in my mind that he will reoffend if he is free. He does not deserve to be free when we never will be.”

A pre-sentence report stated there was a high risk Muir would harm further children, and “serious potential” for him to commit similar offences if he had the opportunity in future.

Muir said he was an alcoholic but had been sober for 14 years.

He theorised that he had not “fully addressed the underlying issues” of that addiction, and simply “shifted” it from alcohol to sex.

“You reported saying you did not set out to do it – it just happened,” said Judge Geoghegan.

“While you may not have set out at first, your behaviour has all the hallmarks of calculated and predatory offending.

“There was planning and premeditation … you took every opportunity to be with them, you engaged in secrecy with them, you regularly exposed both to porn with a view of normalising and encouraging sexual behaviours.

“There was a high degree of manipulation... for your own sexual gratification. It will be with the victims, and with their mother forever.”

Judge Geoghegan sentenced Muir to 12 years and nine months, ordering him to serve half before he was eligible for parole.

“The significant risk you present to the female children of anyone you may be in a relationship with, and the fact your charm and manipulation increases that risk… warrants a minimum non-parole period,” he said.

“What I wish to say to the victims and their mother – and it may come as little or no comfort – is that they have nothing to feel guilty about.

“There is one person, and one person only responsible for why we are here today – and that person is you, Mr Muir.

“The victims have been manipulated by you in your desire to satisfy your perceived needs … sentencing cannot possibly heal the damage that has been done to this family.”