The woman, who "has slowly drifted away" and become more confused and impaired since the assault, was at her Lower North Island rest home in May 2018 when the man approached her and struck up a conversation.
He was at the home visiting a relative.
When the victim returned to her bedroom, he followed her in and shut the door behind him.
He began touching and kissing the victim, who tried unsuccessfully to push him away, but he was "too forceful", according to the summary of facts.
He then closed the curtains so that nobody could see inside, before going back to the victim to continue kissing and touching her.
"At this point, the door opened and a caregiver entered and saw the pair in darkness close together. The caregiver switched on the light," the summary said.
The caregiver noticed the man was red in the face and asked what was going on. When nobody replied, she left to find a manager.
Despite the intrusion, he soon resumed kissing and touching the victim, who again tried and failed to push him away.
He exposed himself to the victim before pulling down her pants and underwear.
He left a short time later.
The caregiver came back with a male nurse and found the victim alone, walking out of the bathroom, wearing different pants.
Her underwear was found in the bin with blood on them.
'I held her while she sobbed time and time again'
A transcript of the victim's evidential interview with police shows her struggling to describe what happened, pausing often to declare "oh God, it's terrible".
The woman called her attacker "a very forceful man", saying he "wouldn't stop".
"I just want to forget everything."
The victim has vascular dementia after suffering a stroke in 2014, and has limited mobility in one of her arms.
Reading her victim impact statement in court, the woman's daughter described how the "bright spark" in her mother's eye was now dull, and how "sadness enveloped her body" the first time she saw her after the assault.
"I held her while she sobbed time and time again."
The woman faltered at times while reading the statement, overcome with emotion, sometimes directing questions at the man in the dock.
The victim started having more falls, the most severe leaving her barely able to move without a wheelchair, she said.
"Our mum as she was has slowly drifted away.
"The accused made a choice, a choice to take advantage of a kind, caring and vulnerable woman. Our mother has inadvertently become part of the #MeToo movement."
In the man's evidential interviews, he initially denied any sexual contact with the victim.
When confronted with the sexual assault allegation and information that blood was found on the victim's underwear, he suggested "perhaps she's done it to herself".
He later confessed, saying the interaction was consensual and that the victim enjoyed it.
He referred to himself and the victim as "private lovers" and talked about their "little secret".
"I wouldn't attack anybody, if she felt threatened I wish she had just said something ... I'll probably regret that for the rest of my life," he said.
"I was mentally unwell when I offended"
The defendant read out a statement in court, saying he deeply regretted his actions, and said the impact of them on himself had been profound.
He apologised to the victim and said what he did was wrong.
"Equally, I apologise to my victim's family. I am so sorry for the pain and hurt I caused you. You were entitled to assume your mum would be left in peace at the rest home. I undermined that."
He also apologised to his wife and the staff at the rest home, as well as his friends, colleagues and students.
"You will be horrified and appalled to learn of my actions," he said.
"I was mentally unwell when I offended. The pressures of overwork and looking after my mother had taken their toll. My actions were totally out of character and shock me."
He said he voluntarily sought counselling and medication after his arrest.
"The counselling I am receiving has helped me understand why I behaved as I did and to ensure I do not behave that way again.
"I never wish to cause such pain and distress to anyone ever again. I give everyone my absolute assurance: I will never reoffend."
Charge downgraded to protect victim
Initially, the man was charged with the more serious crime of unlawful sexual connection.
However, prosecutors later downgraded the charge to indecent assault in an attempt to get him to plead guilty, so the victim could avoid the stress of a trial.
At a sentencing indication hearing last year, Judge Stephen Harrop said the offending was "unbelievable".
"It is difficult to understand and rationalise and it is really completely out of character."
Judge Harrop adopted a starting point for sentencing of two years and nine months in prison, allowing discounts for factors such as the guilty plea, remorse and the man's previous contribution to the community.
With those factors taken into account, Judge Harrop settled on a sentence of eight months home detention and 100 hours of community work, and ordered him to pay $3000 emotional harm reparation.
The man, who was supported by his wife in court, sat in the dock with his eyes closed for much of the hearing, sometimes hunching his shoulders forward and rocking slightly.
His wife sat in the public gallery with her head down, at times putting her face in her hand.
- Additional reporting by Kirsty Johnston
Where to get help:
• If it's an emergency and you feel that you or someone else is at risk, call 111.
• If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline Safe to Talk on: 0800 044 334 or text 4334.
• Alternatively contact your local police station
• If you have been abused, remember it's not your fault.
