(Mis)handling expert evidence – test for the courts

A paper # by The Hon Justice Peter Davis and barrister J.R. Jones puts the spotlight on expert evidence – and shows how inadmissible expert evidence can sneak into court. Dr Bob Moles ## adds the shocking example of the Sue Neill-Fraser case, where “the entirety of the forensic evidence was a complete shambles … that warrants the conviction being overturned,” and is an embarrassment to Tasmania’s legal system. 

It wasn’t much of a case to start with, (as the late Chester Porter QC pointed out) but Sue Neill-Fraser’s 2010 trial for the murder of her partner, Bob Chappell, was riddled with errors – not least the expert evidence that a court paying attention would have declared inadmissible. There are always risks that expert evidence fails one or other of the tests that are meant to guard against misuse and mistakes but this was on an embarrassing scale – and left so through two appeals.

In their paper, “Handling Expert Evidence” The Hon Justice Peter Davis and barrister J.R. Jones could not have imagined the rich trove of examples that case could yield, as we have reported over the years. They have their own: “…it is the practice of the members of the Queensland Police Service Accident Investigation Unit to prepare their reports to appear like scientific papers. That pretence is then exaggerated by having the paper ‘peer reviewed’ by another police officer who is, like the primary author, a so-called ‘crash investigation expert’. As will be explained, most of the opinion evidence sought to be given by officers of the Accident Investigation Unit is inadmissible even if it is ‘peer reviewed’ by another officer who also can’t give admissible evidence.” It would be farcical if it weren’t so serious.

The authors explain that “experts are in the privileged position of being able to give evidence as to their opinion on matters within their expertise. A fundamental precondition to the admissibility of expert opinion evidence is that the opinion must be expressed from a body or science of learning so that the opinion is on matters beyond the common knowledge of members of the community. Experts are, therefore, placed in a position where they are giving evidence about matters not within the general understanding of the jury. That naturally means that expert opinion evidence is likely to be highly persuasive. The basic principles governing the admissibility of expert opinion evidence are well settled. However, their application is often either misunderstood or not the subject of proper consideration and application.”

The trap for the courts is keeping expert evidence within the lanes: “It often happens that an expert witness will be called, will give admissible opinion evidence in relation to the relevant field of expertise, but will then be allowed to stray into other areas, giving completely inadmissible opinion evidence under the guise of his or her ‘expertise’. A related question concerns the limitations on any field of expertise. The jury is the constitutional tribunal of fact. An expert may give evidence on matters beyond the common knowledge of citizens. Matters within the common knowledge of citizens may form the basis of opinions, but the relevant opinion is that of the jury, not of a witness. It is often the case that an expert will stray into expressing opinions on matters of everyday knowledge and experience and therefore impinge upon the function of the jury.”

That was on display in the Sue Neill-Fraser trial, where “the forensic pathologist was called to explain to the jury that a person could be killed by being struck in the head with a heavy metal object. Clearly this comes within the area of what an ordinary person would know and should again have been inadmissible. There was of course no evidence that anyone had in fact been assaulted in that manner and that too would also have rendered the opinion inadmissible. The facts upon which an opinion is based must have been or will be supported by admissible evidence at the trial, otherwise the opinion is irrelevant.”

Then there was “the forensic expert who gave extensive evidence about bloodstains on a boat, had used a preliminary screening test, the results of which were clearly inadmissible,  She was also qualified by the judge to give evidence about DNA results on the basis that she had overheard some experts talking about the matter. In other words the entirety of the forensic evidence in the Neill-Fraser case was a complete shambles and most if not all of it should not have been admitted. There is no doubt at all that these multiple failures warrant the conviction being overturned. And that is without adding the multiple prosecutorial and judicial failures to add to the series of catastrophic failures in this case.”

South Australia’s legal system can’t gloat: there, a pathologist who helped to secure over 400 criminal convictions, and undertook over 10,000 autopsies, had been declared by his employer, in the Supreme Court, to be ‘not qualified to certify cause of death’ and to have ‘no expert qualifications’. Apart from that small fact, notes Dr Moles, “he also gave opinion evidence in many cases which would also have been inadmissible, even if he had been a real expert. For example, in the Bromley case he said that he thought that certain injuries to a face would not have been a kick (a kick he fancied might have loosened teeth) or perhaps a punch or an impact with a barbell. All of this in respect of a body which had been floating around in a river for nearly a week before being discovered. None of the injuries, he suggested, would have been caused during that time in the river.”

As the judge mentions in this paper, these types of explanations by ‘experts’ are no more than the sort of speculations which ordinary people can engage in, and “should not be clothed with the appearance of ‘expertise’.”

# A paper delivered to the Australian Defence Lawyers Alliance Symposium on 18 March, 2022. The Hon Justice Peter Davis is Judge of the Supreme Court of Queensland and President of the Industrial Court of Queensland and the Queensland Industrial Relations Commission. J R Jones is a Barrister of the Supreme Court of Queensland, Murray Gleeson Chambers.

## Dr Bob Moles is Adjunct Associate Professor, College of Business, Government and Law, Flinders University of South Australia