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David Bain, Mark Lundy et al: Are some cases too challenging for juries?

Mark Lundy, who is appealing his conviction for murdering his wife Christine and daughter Amber. Photo/Hagen Hopkins/Getty.

It’s not just the David Bain case where people look at the same evidence and see different things. As technology advances, juries are increasingly expected to grapple with complex scientific evidence and diverging expert opinions before reaching their verdict. In some cases, even lawyers and judges grapple with complex scientific evidence presented in court. Mike White asks whether 12 untrained individuals are capable of dealing with this, or if there’s a better way.

In October last year, Mark Lundy appealed again (unsuccessfully) against his conviction for murdering his wife, Christine, and seven-year-old daughter, Amber. But what was equally on trial in the Court of Appeal over three days was the role and reliability of scientific evidence in New Zealand’s justice system.

At his first trial in 2002, Lundy had been found guilty of the murders largely due to two specks on his shirt which the prosecution claimed were Christine’s brain tissue. This conclusion had been reached after testing using immunohistochemistry (IHC), which had never been employed forensically before. 

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After his conviction was quashed by the Privy Council, the Crown radically altered its case against Lundy, including the timing and scenario for the murders, jettisoning evidence and many witnesses it had insisted were reliable until that point.

But at Lundy’s retrial in 2015, it retained the controversial IHC evidence and added another innovative scientific test on the two specks, involving what’s known as mRNA (messenger RNA). The test, performed in Holland, was so innovative it was created specifically for Lundy’s retrial. Not only had it never been done before, it had never even been peer-reviewed to ascertain its validity or dependability.

The evidence, which suggested the specks on Lundy’s shirt were more likely to have come from a human than other animal, were the subject of considerable controversy before and during Lundy’s retrial as to whether such novel and untested science should be heard by the jury.

But what made the mRNA evidence even more fraught was its extreme complexity, with experts for the Crown and defence arguing in rarefied language that even the lawyers and judge struggled to understand.


At Lundy’s appeal in October, his lawyer, Jonathan Eaton QC, pointed out that the judge had to ask for clarification 16 times during the Crown expert’s evidence. And Eaton said if the Court of Appeal judges read just a few pages of the expert’s evidence, they would have to admit they didn’t understand what was being said. Describing it as unintelligible, he said “the jury were unquestionably drowning in a sea of science”.

How well the jury understood the scientific evidence, which spanned several weeks at Lundy’s retrial, and what weight it had in their decision-making, is unknown. However, Eaton insisted it was utterly wrong for 12 laypeople to have been expected to decipher such complex evidence, weigh the veracity of completely new scientific testing, and decide which of the competing expert views was more credible. “This is an issue that should have been thrashed out between the experts in peer reviews and in conferences, not in front of a jury,” he told the Court of Appeal.

Amber Lundy, who was seven when she was murdered. Photo/Supplied

Complicated scientific and technical evidence has featured in numerous high-profile New Zealand trials, including the cases against David Bain, Scott Watson, Arthur Allan Thomas, David Dougherty, George Gwaze and John Barlow. Forensic scientist Arie Geursen, whose work helped prove David Dougherty was wrongly convicted of rape, and who worked on the Gwaze case, says judges too readily leave it to juries to decide on extremely difficult scientific evidence.

“I don’t know how the jury gets to the bottom of that, quite frankly, how it resolves it. And somehow a better way needs to be found.” Geursen became very aware of these difficulties during the trial of Vicky Calder, in what became known as the “Poisoned Professor” case, where the jury had to decide if eminent plant scientist David Lloyd had been poisoned with acrylamide or suffered a mystery illness.

Christine, Mark and Amber Lundy, circa 2000. Photo/Supplied.

“The courtroom and science are strange bedfellows really,” says Geursen. “The court needs science and expert opinion, but on the other hand, the courtroom is a very bad place to practise science. How does a jury judge whether to believe me or a Crown scientist, or a Crown pathologist versus the defence pathologist, when they take diametrically opposed or intransigent positions? It’s very, very hard to see how juries can put that into context.”

The Lundy case, which Geursen has taken a close interest in, was a clear example of this, with the added burden that the evidence was phenomenally difficult to understand. “You had experts saying the mRNA stuff wasn’t fit for purpose, and you had very strongly held views from scientists that it was. For me, I lean very heavily on the fact that it wasn’t fit for purpose and have believed that for a very long time.”

In August, high-profile UK lawyer Michael Mansfield, who helped defend the Guilford Four and Birmingham Six, who were wrongly convicted of pub bombings, told RNZ’s Kim Hill he utterly disagreed juries couldn’t understand difficult evidence. “I’m an ordinary person, I get my head around it, and juries do understand.”

UK lawyer Michael Mansfield says evidence needs to be explained in a way jurors can grasp. Photo: Victoria Jones/PA Images via Getty .

Mansfield has confronted complex science frequently, including the controversial issue of baby-shaking, and the case of Angela Cannings, wrongly convicted of smothering two of her children. And he insists the crucial issue is having evidence explained in a way jurors can grasp. “It’s not the juries that are at fault, it’s the system that’s at fault in the way the evidence is prepared,” Mansfield stressed, adding it was crucial only “reliable, tested evidence” was used in courts.

New Zealand Criminal Bar Association president Len Andersen agrees that the onus is on lawyers to explain evidence. “You’ve got to be able to put stuff in simple terms, and if you can’t, it’s because you don’t understand it. Often the issue with scientific evidence isn’t that it’s itself complex, but the scientists can’t agree what the significance of it is. And if the scientists can’t agree, it shouldn’t be before a jury, in my mind.”

Andersen says the Lundy case was an example of this, where a succession of judges struggled to decide whether novel tests such as those for mRNA were sufficiently reliable, and essentially left it to the jury to resolve whether it was valid science or not. “How the hell can a jury decide that?” argues Andersen.

When confusing or overly-complex expert evidence is put before juries, such as in Lundy’s trials, he says the risk is that juries will simply ignore it.

Number 30 Karamea Cres, Palmerston North, where Christine Lundy and daughter Amber were found dead in 2000. Photo/Robert Patterson/Getty.

Or worse still, says Whangarei lawyer Emily Henderson, juries may simply rely on which expert they preferred the look of or sounded more convincing. Henderson has co-authored a study on expert witnesses in New Zealand and says it’s a paradox that jurors with no expertise were frequently called on to evaluate complex information that was completely foreign to their lives. The only qualification a juror needs is to be a registered voter. “It really is amateur hour.”

New Zealand courts already recognise juries’ limitations and hold judge-alone trials for complex financial cases, civil trials, and in the Family Court. In these cases, judges have to give reasons for their decisions. But juries give no more than a verdict, with no way of knowing if they understood the evidence, what weight they gave it, or whether they drew accurate conclusions from it, says Henderson.

The way trials are structured, with the Crown presenting its arguments and witnesses first, followed by the defence, doesn’t help juries either, she says. Often, there are days or weeks between experts giving evidence on the same subject, making it difficult for jurors to compare competing arguments. And making sense of these conflicting views often relies on the lawyers understanding the issues and knowing the right questions to ask the experts.

One answer is to “hot-tub” experts, with witnesses for the prosecution and defence appearing at the same time and able to be asked questions by both sides and the judge.

Not only would this decrease the risk of juries forgetting evidence between experts, Henderson says, but it would reduce the scope for witnesses to obfuscate or exaggerate, knowing their peers beside them could immediately pick up mistakes, add crucial context, or raise otherwise ignored issues.

More widely used in Australia, there has been limited hot-tubbing of experts in New Zealand courts, but not in jury trials. One of the best-known uses of it was at the coroner’s hearing into the deaths of infant twins Chris and Cru Kahui. Their father, Chris Kahui, was acquitted of their murder at trial, but a coroner’s inquest found the twins died from brain injuries suffered while they were in the sole custody and care of their father.

Chris Kahui is surrounded by media as he leaves the Auckland High Court after being found not guilty of the murders of his twin sons, Chris and Cru, in June 2006, when they were three months old. Photo/Phil Walter/Getty.

Prosecution lawyer Simon Mount QC says key experts gave evidence separately at Kahui’s trial but appeared together at the coroner’s inquest. He believes this changed how they responded to questions – in a more moderate, collegial way rather than as arbiters of absolute truth – and led to one expert altering crucial evidence he’d given at trial. “So what had been a real bombshell piece of evidence in the criminal context became irrelevant in the coroner’s context.”

While such a change to criminal trials would not happen quickly, Mount feels hot-tubbing experts has real benefits that should be considered. “Any system that produces results that are irrational, unjust or clearly wrong is a dangerous system to have, because it can have a very corrosive effect when you have either guilty people acquitted or innocent people convicted. Our system has shown itself capable of producing both those outcomes, and it’s important to do whatever we can to minimise that.”

Former police fingerprint expert Kevin Sturgeon believes independent experts should be available to the court if the judge, jury, prosecution or defence feel evidence is too complicated. Photo/Ken Downie/North & South

Former police forensic expert Kevin Sturgeon (read his case against David Bain here) says hot-tubbing would still leave juries confused over who to believe, with jurors susceptible to making decisions on superficial things like an expert’s demeanour.

Instead, Sturgeon suggests having independent experts available to the court if the judge, jury, prosecution or defence felt evidence was too complicated. These “amicus experts” could be questioned by all sides in court, adding clarity and context to what the jury has heard. “Because quite obviously, now, people are just stunned – ‘who do I believe?’ And this would give them an independent technical opinion. It may never be used, but it’s there as an option when people are confused.”

It’s a suggestion Simon Mount likes, and he says could be used as part of hot-tubbing. Experts called and paid by the court are used in coroners’ hearings, he notes, and could dilute the inevitable tribalism that occurs between Crown and defence witnesses in criminal trials.

However, Whanganui Crown prosecutor Michele Wilkinson-Smith is more sceptical. “That expert would inevitably be seen by the jury as having more weight than the other experts.”

Wilkinson-Smith helped defend Chris Kahui and has seen experts hot-tubbed in several other cases.

“It has some benefits, it has some disadvantages. The big danger is one expert grabs the floor a bit too much by virtue of their personality rather than necessarily their level of expertise or the validity of their opinion. A dominant personality will dominate.

“Everything in criminal jury trials is about trying to achieve balance. And the minute you tweak something, you unbalance something else. That doesn’t mean we’ve got the balance right now, because we probably haven’t. And it may well be that hot-tubbing, on balance, is better than the current situation, but it will have its downsides as well.”

In jury trials, there would need to be clear guidelines about how hot-tubbing would operate, she says, to prevent it degenerating into a free-for-all between arguing experts.

Having seen trials from both sides, as a prosecutor and defender, Wilkinson-Smith remains largely positive about juries and their ability to assimilate and assess complex evidence, despite others arguing they should be replaced by judges hearing all cases.

“Nothing is that complicated that it can’t be understood. If the jury can’t understand the expert evidence, that’s a failure of the expert and the counsel to explain it. We can get a little patronising towards juries. Twelve brains are generally better than one – no matter how well-trained the brain is.” 

This was published in the March 2018 issue of North & South.