The five High Court judges ruled there was no evidence that Godfrey Zaburoni, 37, had intended to infect the woman, whose name is suppressed, during a two-year relationship that ended in 2008 in Gold Coast city in Queensland state.
One of them, Justice Stephen Gagele, said it was a reasonable possibility that Zaburoni had sex "selfishly for his own gratification, being reckless as to whether or not the complainant might become infected."
Zaburoni was sentenced in 2013 to nine years and six months in prison on a charge of unlawfully transmitting a serious disease with intent to do so.
He will soon be sentenced for the lesser offense of unlawfully doing the woman grievous bodily harm. He had already pleaded guilty to that offense, which carries a 14-year maximum sentence.
Zaburoni came to Australia in 1997 and was diagnosed with HIV the following year. He toured Australia with circus troupes and gained celebrity as a contestant in the TV show "Australia's Got Talent."
He repeatedly told his girlfriend he was HIV-negative until she was diagnosed with the virus in 2009 and confronted him.
She was heavily pregnant when she testified that she would pay for his betrayal for the rest of her life. She told the court that her husband did not have the virus but they would not be sure about their already born baby until it was 18 months old.
State health authorities issued a public warning in 2010 that Zaburoni had admitted to police to having unprotected sex with 12 women in Australia.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.