Jared Savage, who was at the Privy Council hearing in London in June, explains why Mark Lundy's murder convictions were quashed.
The samples were found by the Institute of Environmental Science and Research (ESR) 59 days after the bodies of Christine and Amber were found and pathologists suggested the material might contain cells found only in brain or spinal cord tissue. But the samples were so poorly preserved that they were unable to state this categorically.
The police took the stains to Texas pathologist Dr Rodney Miller. He was also unable to positively identify the tissue under a microscope but conducted an immunohistochemical (IHC) procedure, from which he categorically stated the tissue was from the brain or spinal cord. The IHC procedure had never been used before in this manner, and was powerful evidence that went unchallenged.
At the original trial, the defence conceded the matter was brain tissue and the only issue was how it ended up on the shirt, possibly by accidental contamination during the police investigation.
One of the grounds of the Privy Council appeal was that the expert evidence given by Dr Miller, and others who relied on his opinion, was ''fundamentally flawed''.
Affidavits sworn by Professors Phillip Sheard, Helen Whitwell and Kevin Gatter - all experts in immunohistochemistry - concluded the tissue was poorly preserved and it was impossible to reach any conclusion as to the nature of the material. They concluded the IHC procedure was an ''uncontrolled experiment'' which could not produce a reliable outcome.
What the Privy Council said:
The fresh evidence ''at a minimum'' raised questions about the use of IHC in the forensic setting of a criminal trial.
''[IHC's] widespread and successful use as a diagnostic tool is undisputed but its acceptance as a means of establishing a scientific proposition as an element of proof of guilt remains untested by any experimental or empirical means,'' said the Law Lords.
''While these might not avail as a basis for excluding the evidence of Dr Miller, they certainly sound on the question of what impact the new evidence might have on the safety of the appellant's conviction.''
The 'striking revelation'
The discovery of a previously undisclosed police document was described as a ''striking revelation'' by Lord Hope, one of the Privy Council members.
The report was given to Lundy's legal team in the week before the appeal in London but was never given to defence lawyers at his trial.
The letter was written by the officer in charge of the murder case, Detective Sergeant Ross Grantham, asking a senior officer for funding to visit Dr Miller in the United States to verify the stains on Lundy's polo shirt.
Dr James Pang, a pathologist for the police, thought it was brain tissue but said it was necessary for the evidence to be reviewed by a neuropathologist, Dr Heng Teoh.
Dr Teoh told Mr Grantham the tissue was too degenerated to be identified as brain tissue.
''When he looked at the slide, he commented that he did not think that [Mark Lundy] should be convicted of murder on the strength of the cells in the slide,'' wrote Mr Grantham.
''He further pointed out that just because Christine Lundy's DNA was on his shirt didn't mean a lot as she was his wife.''
Mr Grantham went on to say this was why it was necessary to get Dr Miller's opinion.
But the document was not disclosed to Lundy's lawyers before the 2002 trial, denying a line of inquiry for the defence.
What the Privy Council said:
The Law Lords told Deputy Solicitor-general Cameron Mander it could not accept his submission that the lack of disclosure might not have altered the tactics of Lundy's defence.
''The identification of the specimen from Mr Lundy's shirt as his wife's [central nervous system] tissue was of overwhelming significance. Here was clear evidence of a neuropathologist saying, in effect, that it was impossible to identify the material as CNS tissue; that the cells had degenerated badly; and that Mr Lundy should not be convicted on the strength of this evidence.''
The time of death
The time of death was crucial to the Crown case. According to cellphone records, Lundy had only a three-hour window to make the 300km round trip from Petone to Palmerston North to murder his wife and daughter.
Dr James Pang told the trial jury that he estimated the time of death between 7pm and 7.15pm on the evening of August 29, 2000.
This was solely on the basis of examining the stomach contents of the murder victims and he noted the ''distinctive'' absence of the smell of gastric juices.
Dr Pang did not take the temperatures of the bodies when they were found in the house, or examine them for rigor mortis. He also failed to weigh the stomach contents.
Given the time of the purchase of the meals at McDonald's at 5.38pm and the journey time home, Dr Pang said the digestion process was in the early stages which led to his estimated time of death.
Affidavits were given by several medical professionals, including Prof Bernard Knight, who is a leading world expert in forensic pathology, who reviewed the findings of the Crown experts. Ironically, Prof Knight was cited by Dr Pang during the trial.
He said that the use of stomach contents as an estimate of the time of death was ''so unreliable as to be of little value'' as there are a number of variables which make gastric contents almost useless to determine the timing.
Prof Knight particularly questioned Dr Pang's evidence that ''absence of gastric smell'' was an important factor. He considered this to be ''utterly without foundation and little short of ludicrous'' and he had never heard of this suggestion.
What the Privy Council said:
The board noted that while Dr Pang was cross-examined during the trial, the evidence was not ''subjected to the critical onslaught that is represented by the collective force'' of the expert opinions obtained by Lundy's legal team.
''If their forcefully expressed opinions were accepted, the time of death evidence based on stomach contents would be wholly discredited.''
The Lundy computer alibi
The Lundy family computer was switched off at 10.52pm on August 29. If Mrs Lundy had turned it off at that time, the Privy Council said this would ''plainly be at odds'' with the Crown case.
If that was the case, then the killer could not have been Mark Lundy, as he was with a prostitute at his Petone motel at 11.36pm.
But a police computer expert told the jury there was evidence that the computer's registry file was disordered, which suggested the time on the machine was tampered with.
Maarten Kleintjes demonstrated how it was possible to tamper with the computer and manipulate the ''shut-down'' time on the clock in a way that was undetectable - implying that the computer was shut down earlier than 10.52pm, which gave Lundy an alibi.
He also discounted the possibility that a computer virus could disorder the registry file, saying it was ''far-fetched''.
But a computer expert hired for the Privy Council appeal said there were several ways files could become disordered, including a virus.
Forensic examiner Michael Chappell discovered that the virus-checking program on the Lundy computer was out of date and it was infected with a virus known as a KAK worm. He traced it back to an infected email six weeks before the killings in August 2000 and when he deleted the virus, the registry files returned to their correct order.
His conclusion was there was no evidence of manipulation of the time or date.
Witnesses also said the house lights were on at 11pm, but turned off in the morning.
What the Privy Council said:
If the computer was switched off at 10.51pm, this was potentially an ''important pointer'' towards Lundy's innocence.
The new evidence that the KAK virus was to blame for the disordering of the registry files directly challenged the plausibility that Lundy tampered with the computer time, using a ''highly sophisticated technique which many computer experts are unaware of''.
Read it
Read the Privy Council's full decision online at tinyurl.com/lundyjudgment
