Friday's not guilty verdicts were a tremendous victory for David Bain and a huge validation of Joe Karam's determined 14-year campaign to see an innocent man go free. Paul Holmes, broadcaster and friend to Joe Karam, looks back on the sometimes overwhelming battle for justice.

David Bain is innocent. Robin Bain came in from the caravan that cold Monday morning and killed four sleeping members of his family, then himself.

David Bain, finally, had the trial his case deserved.

Justice Pankhurst allocated three months. It was a trial of enormous detail. After nearly three months of evidence and experts, lead examination and cross examination and determined disputation, it all came down to 12 ordinary New Zealanders. They decided unanimously that David Bain was not guilty of the crimes for which he had been so long held responsible and punished.

And when you think about Robin and David Bain, whose life was it disintegrating in the months before the killings? David's? Hardly. He had friends, he had interests, he had his music and his singing, and he was physically active. The friends have stuck by him always. The prosecution never found anyone to say David had begun to behave oddly. Robin was depressed, looked like death, had lost the ability to do his work, he showered on Sunday and stank by Wednesday.

His wife had booted him out of the home. He had long been having sex with his teenage daughter, an incest that may have begun before she reached her teens. As a relieving headmaster he lived in a filthy, broken-down caravan. Laniet was going home to tell the family everything, she told several people. It was all coming to a head.

The police in Dunedin simply lost sight of the woods for the trees.

The verdicts delivered live to the nation on Friday night sucked the air out of the country. They occupy an unforgettable two minutes in the history of New Zealand. But if Friday was wonderful for David Bain, it was nevertheless a day that belonged to Joe Karam.

I do not know David. I do know Joe. Without Joe Karam there would have been no trial. David would still be rotting in a hole at Christchurch prison, abandoned by most except a few loyal friends, forever a convicted mass murderer. It was Joe, back in the early 1990s, who felt something was wrong. It was Joe Karam who began to study the evidence presented to the original trial. The first thing he realised was that David's defence had been grossly inadequate. Joe went to the prison in Christchurch. He always said that the young man he met there was not anything like the weird, goofy looking young man in the strange jumper in the photograph taken at the time of his arrest. The man in prison in Christchurch was normal, intelligent, sensitive and polite.

Another thing: Joe hated that picture. He knew the prejudice it caused. Joe knew what people thought when they saw it. There was a stunned, grief-stricken David, Joe believed, in that bizarre, bird of paradise, home-knitted jersey someone grabbed for him to wear. David had the look of someone who could have done the killings.

Joe was appalled at the way the family, the Police and the Fire Service colluded to burn the Bain house down in a way that reminded us darkly of the witch trials of Salem, and called up our ancient belief in fire as a cleanser, a banisher of evil.

He often said he could not wait for the day when Bain was released and all the world could see it.

Joe poured himself into this baffling case. Everything he saw, everything he found – and Joe is a brilliant natural investigator – convinced him there had been a travesty of justice. Joe spent hours, weeks, months, locked away, reading, comparing, checking and re-checking, analysing, asking himself questions, working out answers, back to the transcripts of the first trial, back to the police evidence, back to the trial, back to the photographs. He talked to experts. His knowledge became encyclopaedic.

As the money ran out, Joe bought a house at Geraldine in South Canterbury and moved there to think and write. Later, I recall calling by to see him in a bach on the shores of Lake Taupo as I drove from Hawke's Bay to Auckland. Joe was alone, writing his second book, Bain and Beyond.

As public support for Joe's crusade grew, it was Joe who met people in Dunedin who told him things. It was Joe who was approached randomly by people at airports who told him things. These were the jigsaw pieces that began to form a disturbing portrait of a seriously dysfunctional marriage, a father having sex with his daughter, a father who was going downhill fast.

That's when I got to know Joe Karam, when he wrote his first book, David and Goliath, back in the mid-90s. This was when I got to know the All Black fullback who kicked such wonderful goals in the mud with a wet leather ball. A few days after I interviewed him, I invited him over to our home. We talked for several hours. We liked each other. What impressed me most was that he had an answer for every question I put to him. His command of the brief was bottomless. Over the years, he always had an answer that made sense for every question I put.

So began a friendship that was not always close and was sometimes fraught but remains ongoing, although I have not seen Joe since David was released after the convictions were quashed by the Privy Council nearly two years ago.

I checked with Joe yesterday to see whether we are still friends. Joe said, "Our friendship has survived the test of time despite some fractious moments." Meaning, the nights he came over and we drank too much wine and ended up brawling, after which we might not see each other for a couple of months.

The difficulty of being a friend of Joe – and we all found this, I think, those who were close to Joe – was that you had to accept that the David Bain case, and what he saw as a battle for justice, had taken over Joe's life. There was a long period in the late 90s and the fi rst few years of this century when there was no conversation to be had with Joe that was not about David Bain. Joe was so committed to his cause, and so dedicated as to seem obsessed. Well, he was obsessed. Occasionally, I would think of saying to him when we caught up to unwind on a Friday night: "Can we be friends who don't talk about David Bain all night? Is it possible for us to communicate outside this Bain business?"

But I never did. I could never bring myself to. I did not say anything because it would have seemed to demean what he was doing. And I always thought that if I were in David Bain's position, and if I had not killed anyone, than I would want someone like Joe Karam obsessing about me, fi ghting for me day and night, spreading the word every time he opened his mouth. But I suppose there was a time when people avoided Joe. And there were a couple of times, when what I said on the radio and what I wrote in newspapers crossed the line demanded by my jobs. I had, however, tremendous admiration for him, just as I admire anyone who battles so courageously for the underdog. Joseph is a good man, possibly a great one, but he is also an intense man.

He gave his life to the cause. He spent everything he had. His boys worried about him, the way the case had overtaken his life. They love him dearly.

As his material wealth declined, so the support his boys gave him increased. They became part of the campaign. Richard was always there, Matthew was a barrister on Michael Reed's legal team in Christchurch.

Did Karam ever think about throwing in the towel? I do not know. I doubt it. In early 2004, a few months after the Court of Appeal threw out David's plea for the second time, we met for a coffee. He felt so helpless.

"No," he told me yesterday, "I never thought of giving up. When I met you that day I was wondering which way to move forward rather than whether to move forward."

Remember, by this time, two Courts of Appeal had refused Bain's petitions. A retired High Court Judge had examined Karam's concerns and rejected them. So had the Police Complaints Authority. It was a bad time.

"There were two worst moments. The first was the North and South article that portrayed me as a flake. Well, it was worse than that. It said that Karam had seen all of the evidence and was charging ahead promoting a proposition I knew to be false. Namely, that David was innocent." Joe sued. North and South settled out of court.

"The second of the worst times" he says, "was after the Court of Appeal decision in 2003."

Nevertheless, Karam soon had another legal team up and running and they began to work on taking the case to the Privy Council.

Joe says there were four magic moments in the whole journey. "The first was winning leave to appeal to the Privy Council. The second was winning the hearing at the Privy Council."

London was a revelation for Joe. At the Privy Council, at 9 Downing St, he watched in amazement and gratitude as the Law Lords, Baroness Hale and Lord Bingham demonstrated a detailed knowledge of the ins and outs of this baffling, confusing case and asked very tough questions of the prosecution. It was there he had his first great triumph, the quashing of the rulings of the New Zealand courts.

Joe respects only evidence. When people, including a certain prominent author spoke of black magic rituals in Papua New Guinea, Joe's eyes dripped contempt. Show me the evidence, Joe would say. Go to the evidence and bother me only with hard evidence, not the might-bes and the could-have-beens. Even his detractors came to see this. Joe could not be dismissed as some kind of ex-All Black businessman on a mission. Joe researched and followed the signs. Finally, the highest court in the Commonwealth accepted that his research could not be ignored.

Joe's third magic moment was when, five days after the Privy Council decision, David Bain walked from prison a free man, albeit one on bail.

Joe took over David's welfare. It was Joe who put him up and hooked him up. Joe says: "David has never lied to me."

He tells me this has been the toughest 18 months of the entire 14 years he has been campaigning. On a cellphone the other night, before the jury went out to consider their decision, he told me darkly that he and his team no longer had meaningful discussions on their cellphones. Neither did they talk about the case any more in their hotel rooms.

Joe did not want another trial after all this time. He believed David could not get a fair one. In fact, the trial returned a brilliant result, full acquittal on all charges. Michael Reed has been incisive in defence, thoroughly in charge of the detail. But without Joe Karam, there would not have been this exhaustive affair. Without Joe Karam, David Bain would never have had a chance.

Oh, and the fourth magic moment? That came late on Friday afternoon, in the terrifying stillness of the packed High Court in Christchurch, where not a hair moved as the jury forewoman stood and uttered 10 words Joe Karam and David Bain had waited so long to hear.

"Not guilty. Not guilty. Not guilty. Not guilty. Not guilty."

It took the ferocious and dogged energy of one man to free David Bain. His was one magnificent obsession.