Dubbed the 'HIV predator', Mills would insist to sexual partners he was "safe'' or "clean'' despite testing positive for HIV in May 2007.
He would persuade partners to have unprotected sex. If they did use protection, he would deliberately rip or remove the condom.
An inquest at the Auckland District Court began this morning, to allow Coroner Katherine Greig to rule and potentially make recommendations based on his death.
Detective Sergeant Andrew King, in charge of the Auckland sexual assault team at the time of the investigation, told the court of the circumstances before Mills' arrest.
He had been rung by a concerned Auckland doctor, who had seen several males claiming they could have contacted HIV from Mills.
Following an article on GayNZ.com, a complainant came forward.
"It rapidly became obvious that Mr Mills was extremely sexually promiscuous,'' Mr King said.
He was of a high public health risk, having met and slept with people through dating websites, telephone websites, gay clubs and saunas and bars, he said.
A "dump'' of his cellphone records showed 60,000 text messages were sent or received over the prior six months.
"It was not possible to try to contact all people he had communicated with.''
He was arrested in May 2009 after checking into a motel under a false name, and appeared in court the next day.
Fifty-seven people he had slept with were tested for HIV at a single Auckland testing centre, Mr King said.
At the time of his death, police were also considering laying charges for sexual violation and drug-assisted sexual assaults.
The number of HIV-negative complainants had to be limited, Mr King said. The eldest of the complainants was 44-years-old, and the youngest 18.
Mills was found dead in his prison cell at 5am on the day he was due to appear in court.
He died in circumstances that were not suspicious, and no other people were involved.
He left an 11-page note, outlining his concerns and anxiety about his circumstances, court appearances and growing public interest in his case.
Mills was taking anti-depressants at the time of his death, and was regularly assessed after court appearances and any change in circumstances.
On one occasion, it was noted he was "sad and worried'' about details of his case being released. On another, he reported being verbally abused and threatened by fellow inmates.
The assessments constantly declared him to not be at risk of self-harm.
