"In her heart she knew that he would reoffend [if released]," she said.
"It's taken more than five long years and a lot of stress ... but it's important to stand up and come forward about rape and sexual abuse."
Justice David Collins said Keats' offending was characterised by "serious violence, abusiveness, a sense of entitlement and a determination to humiliate his victims".
In 2010, Keats was jailed for eight years for raping his former partner when she ended their relationship.
He was paroled in 2016 and got work as a truck driver with The Salvation Army despite the organisation knowing of his background.
Through that employment, the predator met the woman.
"Mr Keats targeted a vulnerable victim who naively looked for positive features in those whom she encountered and was willing to place misguided trust in [him]," Justice Collins said.
A consensual relationship began, but the man quickly became overbearing and aggressive.
He was found guilty on six counts of rape and four of sexual violation by unlawful sexual connection following a judge-alone trial at the Dunedin District Court.
The victim spoke of episodes during which Keats would throttle her and there were several occasions he woke her at night and demanded she submit to sex even though she was tired and in pain.
Clinicians who interviewed the sex offender agreed he presented a serious threat to the public. In one case, he refused to speak to the psychiatrist because she was a woman.
On a psychopathy checklist Keats showed a very high risk of reoffending which was "likely to be sustained over the long term", another concluded.
"There is no evidence Mr Keats is ready to begin therapy and treatment when he shows no signs of understanding the magnitude of his issues," Justice Collins said.
"The escalating nature of Mr Keats' offending is a disturbing feature of his case. His offending fully justified the imposition of a sentence of preventive detention in order to protect the community from the strong likelihood of the risk he poses to the future safety of women."
The court dismissed the prisoner's own appeal of his convictions, ruling the grounds lacked any merit.
The Salvation Army said it was "extremely concerned" Keats was given a job and launched an investigation after the Otago Daily Times made inquiries.
One of the charity's national directors, Lynette Hutson, said it was "deeply sorry" about what happened but a later review appeared to clear it of blame.
While the report was not provided to the ODT, The Salvation Army said it found "the actions or omissions did not contribute significantly to enabling Keats' offending".
Keats will go before the Parole Board in 2025.
SEXUAL HARM - DO YOU NEED 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 contact the Safe to Talk confidential crisis helpline on:
• Text 4334 and they will respond
• Email support@safetotalk.nz
• Visit https://safetotalk.nz/contact-us/ for an online chat
Alternatively contact your local police station - click here for a list.
