Key Points:

Robin Bain swung his legs out of bed, cosy from his cot in the caravan at the rear of the family home. It was a chill Dunedin morning - about 6am - and Robin's early entry to his final hour on Earth was as cold and creaky as any 58-year-old might find it.

It was a grubby little cabin he left, braced on metal stands to stop it rolling down the steep Andersons Bay hill and surrounded by the detritus of a disordered life. At his bedside, an Agatha Christie collection of short stories. The last of five was called Death Comes as the End, the tale of a son who kills his family to claim the inheritance.

This morning, June 20, 1994, Robin shuffles through the solitary hour before dawn to the family home, where he's becoming increasingly a stranger. Inside, his wife Margaret and three of their four children - Stephen, 14, Laniet, 17, and Arawa, 18 - sleep. David, 22, has already risen and is out in the cool morning delivering news-papers. Robin has 45 minutes to commit his dark deed. He changes out of his trackpants, sweatshirt and jersey into other clothes. Later, he will write a farewell message to David on the family computer: "Sorry. You are the only one who deserved to stay." Now, he is intent on murder - and murder in a way that will lead authorities to charge "the only one who deserved to stay".

Ignoring his urge to urinate, Robin goes into David's room and gets the .22 his son hunts hares with. He knows the gun - had sighted it for David some months earlier. He finds the key to the trigger-guard in a jar on David's desk and digs into his son's drawer to find a pair of white opera gloves. His own are still in the caravan.

Then Robin begins to murder. He shoots Laniet three times, the Whisper ammunition and silencer preserving the still of the morning. Then Margaret dies - a single shot to the head - and he heads for Stephen's room. It is horrid. The boy dies but leaves Robin covered in blood. He takes off David's gloves and leaves them there, walking downstairs to kill Arawa in her room.

He decides he has to clean himself. He washes, puts his bloody clothes in the basket and changes back into his overnight clothes. He has been wearing socks but now puts shoes on.

Robin then heads for the lounge, where he sits and waits. Perhaps he intends to kill David, or he could simply be contemplating his final moments. Still ignoring nature's call, Robin turns on the computer and taps out the message to David. Then, right-handed Robin takes the rifle in his left hand, holds it far and high to one side as if it were a pistol and pulls the trigger. Somehow he avoids getting blood on his hands and fingerprints on the gun. Minutes later, David returns from his morning run. He bundles his father's bloody clothes into the washing machine, sorting light and dark clothing, and unwittingly places a bloody handprint on the front of the machine. He washes his hands but manages to avoid disturbing other blood spots left in the basin. He begins to discover the bodies; after about 25 minutes, he calls for help.

That morning in Dunedin has been a case of square pegs and round holes. The theory - and this dramatisation is just one of many - that Robin Bain carried out the morning massacre is a difficult one to wrestle into place.

Even Joe Karam, David Bain's great defender, has offered alternatives in the past. In a July 1997 meeting with police and staff from the Police Complaints Authority, who were investigating Karam's allegations of police failure, he spoke of the possibility of a second weapon being used against Laniet. Karam had an expert witness who described one of the wounds as so large, it would have been inflicted by a .45 calibre pistol. Police ruled out the possibility. The review report reads: "Mr Karam said he was worried the murderer could still be walking the streets of Dunedin. He said he did not set out in his book to prove Robin Bain was the killer. His intention, he said, was to show the police investigation never excluded him from the crime."

But no matter - Karam is sure, as his 12-year campaign shows, that David Bain did not do it. After considering the Crown case, Karam wrote to the Herald on Sunday stating: "The over-arching point is that all of this evidence of the Crown is totally consistent with David being the 'finder' of his dead family."

David Bain's victory before the Privy Council found that the system had failed him, that evidence presented in the original case was not heard when it should have been, or that the wrong direction or inference may have been taken from that evidence. There was new evidence which should have been accorded weight but wasn't. The answer, said the Privy Council, was a retrial. And this time, all the evidence should be heard.

Should the retrial go ahead and the Crown meet David Bain again in court to decide guilt or innocence, the jury will have before it evidence gleaned from 12 years of relentless inquiry by Karam.

It has not been a one-way process. Even as Karam has put forward new questions, the police have found fresh answers.

This week, in Dunedin, five detectives are compiling evidence put before the first jury, and that discovered since by police. The Crown Law Office is reviewing the evidence, expecting a retrial and building the framework for the case against David Bain.

These are likely to be its strongest elements.

THE FIGHT WITH STEPHEN
The Crown: The bedroom was seriously disturbed by the fight between Stephen and the killer. The initial shot fired at Stephen passed through his hand and shaved his head, giving him a bloody scalp wound. Both Robin and David had evidence of injury, although Robin's injuries were around his fingers - not knuckles - and were partially healed at the time of his death. David had fresh injuries when police arrived - bruises on his face, an abrasion above his right eye and a scraped knee. A piece of skin police say matches David's knee was found in the room, although DNA testing at the time shows it could have come from any of the children. Stephen was aged 14 at the time of his death - the Crown would submit that the physiques of the assailant would play a part; Robin was 58, heavily depressed and unfit, while David was 22, fit, tall and strong.

The defence: In Bain and Beyond, Karam wrote, the bruise on David was above his right eye, when it was the left lens that was alleged to have been knocked out of his glasses during the struggle. Further: "Such minor injuries as David had were consistent with those he would have sustained blundering around the darkened untidy house in a state of shock." Karam also noted that David had collapsed in the presence of police, "banging his head against the wall". He also wrote that expert evidence of Australian pathologists had considered the injuries to Robin's hands, described as "semi-healed"; their conclusion was opposite to the Crown's. In an email to the Herald on Sunday, Karam listed Robin's injuries: right hand: abrasion to knuckle of middle finger, back of ring finger and a large bruise to area on back of hand to rear of middle finger; left hand: big abrasion to knuckle of thumb, two abrasions to left index finger, one at knuckle region and one at top joint area. "In respect to the piece of skin referred to, this was debunked at David's original trial and is not even mentioned now in any of the Crown submissions at either our Court of Appeal or the Privy Council."

DAVID BAIN'S CLOTHING
The Crown: Both Robin and David Bain were found to have blood-stained clothes, although in Robin's case, all blood tested belonged to him or, according to the police review in 1997, possibly to David. The bloodstains identified on David's clothing were matched by police at the trial to Stephen, Arawa or Laniet. By the time a post-trial police and Police Complaints Authority review had been completed in 1997, ESR scientists stated the blood could have come from Stephen, and not from any other member of the Bain family. Scientists tested a blood stain on David's shorts which they submitted had soaked through an outer item of clothing to become lodged in the seam in the crotch. Smears of blood on David's T-shirt were also tested by ESR scientists. The post-trial review stated that three of those smears - front left side, middle of the back and upper left back - could have come only from Stephen, and not from any other member of the family. The technology to carry out this test was not available in 1994.

The defence: The "stain" on David's shorts was "so minute as to be undetectable by the naked eye", Karam wrote in Bain and Beyond. Writing to the Herald on Sunday, he stated: "The only mention that the smear on the shorts 'soaked through outer garments' came in the Court of Appeal decision which has also been overturned. The Crown or police have not to my knowledge advanced this theory, and for good reason." Karam wrote that the only blood on David's T-shirt was light smearing on the lower back - and that blood on his lower back was said at trial by ESR scientists to be "old blood". Karam also said he had not seen any evidence stating that the blood on Robin's clothes was possibly David's. Karam has previously stated that blood on David's shirt was consistent with "brushing against blood stained surfaces... but quite inconsistent with what would be expected to be on his clothes if he had shot five people at point-blank range, and been involved in a bloody struggle as alleged".

THE OPERA GLOVES
The Crown: The white gloves worn by the offender had been taken out of a drawer in David's room. Robin had his own similar white gloves, which were left undisturbed in his caravan. The gloves were found blood-soaked in Stephen's room under the bed - the Crown believed they were removed to clear a round trapped in the rifle and were pushed under the bed during the fight that followed.

The defence: In David and Goliath, Karam's first book on the case, he wrote that there was no evidence offered by the Crown that David had worn the gloves that day. "They were readily available to any other person who looked in David's drawer. Nothing links David to the gloves except they were his." Karam asked why David, if he was trying to frame Robin "as the Crown suggests", would leave his own gloves in Stephen's room. "This is another absurdity in the Crown case... why didn't he wash them and dispose of them, burn them or at least remove them from the scene." Karam also notes, in Bain and Beyond, that there were possible traces of blood in fingernail scrapings taken from Robin that were never made available to the defence in the trial.

THE RIFLE
The Crown: The only prints on the gun were Stephen's, fending off the killer, and David's, which could well have been from an earlier hunting expedition. However, there were no prints belonging to Robin Bain. The police and Police Complaints Authority team that reviewed the original inquiry stated: "If Robin Bain had shot himself it would be expected to find his fingerprints on the weapon." Also, while there were a few specks of blood on Robin's hands, the reviewers found "no blood on Robin's hands consistent with him having handled the bloodied rifle when he committed suicide". The rifle was found to have Stephen's blood on it in a number of places, and it also showed signs that an attempt had been made to wipe the weapon clean.

The defence: In Bain and Beyond, Karam wrote that data from United States and Australian experts showed it was "very rare" to find fingerprints on a weapon used to commit a murder or suicide. "It is only in about two per cent of cases that such fingerprints are found." In an email to the Herald on Sunday, Karam wrote: "There were many prints on the gun which did not have sufficient detail to be identified with certainty. This dispels the belated suggestion that the rifle had been 'wiped'." He said there were more than "specks" of blood on Robin's hands. "In fact there was a large smear of blood on the heel of his left thumb (untested and not photographed), a smear of blood on the underside of his left little finger (ditto), a splash of blood on his left index fingernail, as well as numerous specks [and] light smears of blood on the back of various fingers and of course the blood in his fingernail scrapings. None of this was tested and the samples that were taken no longer exist, so we are told. No explanation for its presence has ever been forthcoming."

BLOODY HAND PRINTS
The Crown: Blood-stained clothing was laundered the morning of the murders. Blood stains were found on the washing machine and the wash basin, and towels had also been stained, as if someone had tried to wash blood from themselves. David's bloodied palm-print was found on the washing machine, although no sign of blood was found on his hands - he told officers he had washed them after the paper round to remove printers' ink. Blood spots in the wash basin were also inconsistent with David's statements on when he had washed his hands. The Crown stated that if Robin had washed his hands in the basin to remove blood from his hands, then the spots in the basin would have been removed or diluted when David returned from his paper round and used the basin. Robin's hands were also inspected by a detective, in charge of the victims, who found dirt around the fingernails and in the creases of his hands. They did not appear to have been washed. There were small specks on Robin Bain's hands - but nothing of the scale expected if he had held the rifle to his head.

The defence: There is no evidence, writes Karam in Bain and Beyond, that the "blood-stained clothes" were laundered. "This is speculation." Also, he writes, an examination of the evidence shows the palm print that was described as being made in blood "was not red in colour and was only visible after various processes were used which give reactions to substances other than blood". His lawyer, Michael Reed, QC, also stated to a Herald on Sunday reader panel this month that it was unclear if the substance was blood. He added: "The laundry/bathroom was dingy, and if it is his palm print in blood (which is not clear), then he must have touched some bloodied clothes in the laundry basket." Karam points out that Margaret Bain's diaries stated that David usually did the washing, so "it is not surprising his palm print was on the machine". Also in Bain and Beyond, Karam wrote that the inference drawn by the Crown from the blood spots was illogical. "With six people using a hand basin, spots of blood are common from activities like cleaning teeth or shaving." Karam, in discussing other evidence, also raised questions about blood under Robin's fingernails and the testing of a few spots of blood on Robin's hands. In an email to the Herald on Sunday, he states that blood found on a towel there "has since been tested by the Crown (DNA) and found to be Robin's".

GLASS LENS
The Crown: There has been much debate around the lens found in Stephen's room and the glasses frame and remaining lens found in David's room. It was mistakenly identified in the wrong part of the room in the original trial, but the police review team maintains it is still a critical part of the case. David has limited vision without glasses, and his own were being repaired. The Crown case maintained that he had worn these glasses - an old pair - to help with his vision while he waited for his own to be repaired. The Crown maintains that the glass was dislodged during David's struggle with Stephen, and it ended up covered in dust, under an ice skate and covered in clothing during the fight, where police found it later.

The defence: In Bain and Beyond, Karam writes that the position of the lens - under an ice skate that was under clothing - was a place "where it could not possibly have fallen". He also writes that there is no evidence that David was wearing those glasses that weekend, and there is evidence he was wearing no glasses at all. The glasses have no blood, hair or fingerprints to link them to the events of that morning. In an email to the Herald on Sunday, Karam wrote: "There is evidence (three separate witnesses) not called at trial that people with David on the Friday night and all day Sunday before the killings say he was not wearing any glasses because his were broken on the Thursday. Why then would he want to wear them to shoot people at point-blank range in the dark?"

NATURE'S CALL
The Crown: Robin Bain was found with a full bladder. The urine collection was established to have occurred overnight. It is significant because of the amount of time Robin would have ignored nature's call, as there was a time lapse between his death and the earlier death of the others in the house. The Crown has claimed that Robin would have been unable to resist the urge to urinate over a period beginning at 4.30am, when the first murder was committed - and a hard-fought battle with Stephen - through to about two hours later, when he was killed. Instead, the Crown sub-mits he rose and went to the lounge to pray, where he was shot and killed.

The defence: David's defence lawyer, Michael Reed, QC, told a Herald on Sunday reader panel this month that the Crown made little mention of the "bladder issue" in the Privy Council "as it is such a silly point for them". "There is medical evidence that people overlook any urge to urinate in a stress situation. We all know that when we are distracted or very busy, we forget to urinate." Equally, he wrote, the police scenario stated that Robin was intending to pray for at least 45 minutes without urinating. "On the police scenario (which is wrong) why would Robin not first urinate?" Karam writes: "It is evidence that he was stressed and distracted from his normal routine, and therefore supports the case against Robin, not for him."

GURGLING IN DEATH
The Crown: David said he went into Laniet's room when he returned from his paper round and saw her lying dead. His next statement - that he heard gurgling noises emitting from her - has become a point of controversy between the defence and prosecution. However, the Crown has maintained through its 1997 review that dead people do not gurgle and that Laniet would have died instantly on the second or third shot to her head. For there to be gurgling, the post-trial review expert said, there would have to have been breath. And, to hear the gurgling sounds, David must have been nearby for the second or third shots while Laniet was still breathing.

The defence: Karam wrote to the Herald on Sunday: "This issue has developed entirely since the post-trial review. The Crown completely missed or ignored the evidence of the entry wound size in Laniet's head and the fact that two bullet fragments with cotton fibres attached were found external to her body, even though there was no exit wound. The effect of this evidence is that the first shot was instantly fatal, and so if David heard gurgling, then it was post mortem and entirely innocent. Uncontroverted evidence for the defence is that dead bodies do gurgle. Any hunter will know this!"

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THE POINTS THE PRIVY COUNCIL MADE

The foundations of the Crown case have already been shaken in attempts to convince the Privy Council of David's guilt. While the law lords found nine points on which to base their finding that there had been a miscarriage of justice, they also cut down three of the main pegs of the Crown case.

The law lords stated that the Crown's case on appeal was "to emphasise the strength of the many facts pointing clearly towards David's guilt". The Privy Council said the issue of guilt was one for a jury, not for an appeal court. It said the issue for the jury was more whether there was evidence which would give it reason to decline a conviction, rather than evidence it would use to convict. And, finally, that a fair trial meant a jury should hear all the evidence before returning a verdict.

But the law lords felt compelled to consider and make comment on "three key points which the third Court of Appeal identified as establishing David's guilt all but conclusively". The law lords' findings cut the Crown's legal legs from beneath it and handed a huge victory to David Bain and his defence.

Should the Crown pursue a retrial, it will have to consider evidence it always maintained as compelling.

A. The trigger lock: The rifle belonged to David and had been taken from David's room. A trigger lock which stopped the weapon from firing was unlocked with a key hidden in David's room, and there was no sign the room had been searched to find it.

The law lords: The Privy Council said that the Crown leaned too heavily on its claim that only David knew there was a spare key to the trigger lock, or that the key was hard to find. It said that it could be expected that Robin had a greater knowledge of firearms, would know there were two keys and that the jar on David's desk was an obvious place to look for a key. Further, there were 20 spent rounds in Robin's caravan, including some ammunition of the same type used in the murders. This indicates that Robin might have used the rifle without David's knowledge in the past.

B. The blood-stained rifle: David's fingerprints were found on the rifle in a carrying position and it was suggested to the Court of Appeal the prints had been left there at the same time as the murders had occurred. Karam has since maintained the prints could well have come from a hunting expedition which took place months before the murders.

The law lords: It was not one of the 12 main points in the Crown case and it was not a point the judge drew to the attention of the jury. There was no reason to believe it might have been in the jury's mind, the law lords found, and "it can hardly be fair to rely on it for the first time on appeal eight and a half years after the trial".

C. The spare magazine: A spare magazine for the murder weapon was found on its narrow edge almost touching Robin's right hand. The prosecution argued it was unlikely to have fallen and landed on its edge but must have been placed there.

The law lords: Again the lords found that it was an issue for the jury to decide, and not an issue which the Court of Appeal should have ruled on. "It could have been David. But there is no compelling reason why it could not have been Robin."

It also ruled on nine points brought by the defence, which it ruled as taken together "compels the conclusion that a substantial miscarriage of justice has actually occurred in this case". These included Robin's mental state which, it said, the jury should have had the chance to consider, including that he was becoming increasingly depressed.

The law lords said the evidence did not alter facts which were still argued over but might alter the weight the jury gave to those facts.

Motive: The law lords viewed statements indicating that Robin was having a sexual relationship of some sort with his daughter Laniet, and said the jury should be able to weigh the information with the other evidence because revelations of sex offences against his daughter combined with deep depression might allow it to "conclude that this could have driven him to commit these acts of horrific violence".

Luminoil sock prints: A sock print found outside Margaret Bain's room could have fitted Robin and not David. If the jury were to accept this, it would suggest Robin had visited parts of the house the Crown said he did not.

The computer switch-on time: The jury should not have been told as fact that the computer was switched on at 6.44am. It could have been earlier and it could have been later.

The time of David's return home: There was evidence which might suggest an eyewitness sighting of David the morning of the murders was more precise than the jury heard.

The glasses: Cross-examination of David over ownership of the glasses - which was immaterial evidence - could have impacted on his credibility.

The left-hand lens: The original trial was told the missing lens from glasses found in David's room was found in a particular place in Stephen's room. It was actually found in another part of the room. The Privy Council says it is important what the jury would have made of this.

David's bloodied fingerprints on the rifle: New blood work shows it could have been blood from a possum or rabbit.

Laniet's gurgling: The evidence of David that he heard his sister Laniet gurgling is set against expert evidence after that trial that post-mortem gurgling was possible.