Those of us who like our murder mysteries without the loose ends will come away from the David Bain retrial disappointed. There is no satisfying denouement to close this tragic story - no sense that we have unravelled the complex plot twists to uncover the truth, no comforting certainty that justice has been delivered. There is only a verdict that many of us will continue to debate for some time.

Fourteen years after the judge in the first trial said in the opening line of his summing up, "Who did it? David Bain? Robin Bain?" we are no closer to the truth. Everyone has an opinion - but only David Bain knows the answer.

The armchair detectives have only questions. Did Laniet really have an incestuous relationship with her father? Did the religious Robin really care more about the stains on his clothes than the stain on his soul, such that he would have changed out of bloodstained clothes, just so he could meet God in clean ones, as the defence suggested? Witnesses said Robin's school desk was in disarray, he was too depressed even to open his mail, but after the killings he was apparently thoughtful enough to deposit his bloodied clothes in the laundry, where David would later wash them and his own clothes without noticing the blood (thus providing a reason for why Robin didn't have any of his murdered family's blood on the clothes and socks he died in).

It's no wonder this case has captured the public imagination since David Bain called 111 on a cold Monday morning in June 1994 to say he'd returned home from his paper round to find his entire family dead. When the police arrested the gangly 22-year-old university student, he looked, at first, an unlikely suspect.

Since then we've come to know something of his family - a family that looked normal and unremarkable from the outside, but whose squalid, disordered home betrayed the dysfunction the rest of the world didn't see.

Robin and Margaret had been missionaries in Papua New Guinea but had seemed to struggle to settle back into life in Dunedin. By 1994, their house and life were crumbling around them. Robin, estranged from his wife, was spending three nights a week at the Taieri schoolhouse where he was principal, and sleeping in a caravan outside the house when he was home on weekends and Mondays. Laniet, 18, was working as a prostitute and telling people she barely knew that she was having sex with her father, that she'd given birth to babies and had had an abortion. Margaret seemed to be leaning towards the occult, using a pendulum to make everyday decisions and obsessing about demons.

And, yet, the family had produced a head girl in Arawa, then 19, and studying to be a teacher. Stephen, at 14, was popular, and a keen sportsman. And David, after a couple of aimless years on the dole, seemed to be sorting himself out. He was studying music and classics at Otago University, his operatic talent was beginning to draw attention, and he had a new girlfriend. Life was finally looking up.

If Laniet's alleged threat to blow the lid on the supposed dirty family secret was a motive for Robin killing his wife and children and then himself, it could also have been seen as "giving David a motive or reason as well", the Court of Appeal noted in its 2003 decision, "in wishing to destroy those in his family he considered should not survive".

Bain's supporters, including his fiercest advocate, Joe Karam, have shown unswerving faith in their man.

On Campbell Live, one supporter said she believed in David Bain's innocence "because of my understanding of the way that people function, of people's nature, and it made no sense at all that David could have done this, whereas the story that he told made absolute sense".

Another said she'd sat through the first trial "and anyone who was there would know that the story that the police put forward was just ridiculous. To say that a man could stop and start killing like that ... absolutely doesn't make sense".

Whatever the truth, a jury of seven men and five women has found Bain not guilty of the murders, and after 15 years, two trials, two failed appeals and a Privy Council decision, that must be the end of it.

David Bain is a free man, Karam gets to say he was right all along, which has to compensate for the heavy personal and financial price he has paid, and David's loyal supporters can feel that a wrong has finally been put right.

Inevitably, there has been criticism of the police investigation - flawed, yes, but the police had strong evidence leading them away from Robin and towards David - and of the decision by the Solicitor-General to retry the case.

It's inconceivable that David Bain should have walked free without a jury assessing all the evidence.

And, after all, five people died. The retrial may not have uncovered the truth, but they deserved our best efforts.