A Cambridge man’s long fight for justice for his brother who fell to his death 35 years ago from a clifftop in Sydney, Australia, ended Thursday when a man pleaded guilty to manslaughter in a courtroom in New South Wales.

Steve Johnson watched a livestream of the proceedings as Scott White admitted to killing Scott Johnson, a confession that came three months after his conviction on a murder charge from a previous trial was overturned by an Australian appeals court.

“It was certainly the most emotional moment I’ve had yet, to see and hear him actually openly admit to having killed my brother,’’ Steve Johnson said in a phone interview Thursday evening.

Johnson had fought for years to overturn an initial finding that his brother, a 27-year-old mathematician and doctoral student and gay man, had taken his own life in 1988, in a fall from a clifftop known as a gay meeting place.

White, who was arrested for the killing in 2020, stunned his lawyers early last year when he pleaded guilty to a murder charge. Almost immediately, White attempted to reverse his plea. But in May, a judge ordered White to serve 12 years and seven months in prison. However, in November, an Australian appeals court overturned White’s conviction.

New evidence linking White to the crime came in October when police intercepted a prison phone call between White and a niece in which he confessed to striking his victim at the clifftop, Johnson said.

“The fact that that phone call was recorded brought him and his defense team to the table,’’ Steve Johnson said. “So, for the past two months, we’ve been negotiating the terms of the plea.’’

White on Thursday pleaded not guilty to murder and guilty to manslaughter. Prosecutors had earlier agreed with White’s lawyers to accept the plea.

Police Deputy Chief Inspector Peter Yeomans told reporters outside the court that the conviction vindicated the Johnson family’s long fight for justice.

“Look, a very emotional day for everyone, especially the Johnson family, who’ve been through a very traumatic time over the past 34 years and today really vindicates that family, what they’ve done over many, many years,’’ Yeomans said.

Steve Johnson said White’s written confession, submitted as part of the plea deal, provides answers that he has long sought, he said.

“He confirmed it all, and admitted to it all, and said he killed my brother, and he threw the first punch, and maybe it was the only punch, and sent my brother over the cliff,’’ he said.

Steve Johnson, a wealthy tech entrepreneur who once offered to pay $1 million in Australian dollars as a reward for an arrest in the case, said arriving at the manslaughter plea was “like a miracle.’’

“‘Closure’s not a word that I like to use, but I do have to say, this feels like closure,’’ he said.

Scott Johnson’s death was initially ruled a suicide. But a coroner ruled in 2017 that Scott Johnson “fell from the clifftop as a result of actual or threatened violence’’ by unknown assailants who “attacked him because they perceived him to be homosexual.’’

The coroner also found that gangs of men roamed various Sydney locations in search of gay men to assault, resulting in the deaths of some victims. Some people were also robbed.

It was the third inquest into the tragedy following pressure from the family. After the coroner had initially ruled in 1989 that Johnson had taken his own life, a second coroner in 2012 could not explain how he died.

Steve Johnson praised Australian authorities for their recent work, including “the police investigator that never gave up, even while the first conviction was overturned’’ and who found the recording of White’s confession.

But he said some Australian police in the late 1980s turned a blind eye to assaults and killings of gay men.

“The person who just confessed yesterday would have been on a very short list of five or six suspects back in 1988,’’ he said. This could have been solved in weeks back in the day.’’

Material from the Associated Press was used in this report. Jeremy Fox can be reached at jeremy.fox@globe.com.