Use of expert witnesses a double-edged sword

The court process and support structures around the use of expert witnesses leave a lot to be desired, particularly in child abuse or neglect cases, researchers have found.

Research by Dr Emily Henderson, a criminal prosecutor from Whangarei, and Dr Fred Seymour, a psychology professor at Auckland University, has highlighted problems around juries’ difficulties in comprehending and evaluating scientific evidence.

The report ‘Expert witnesses under examination on the New Zealand criminal and family courts’ also found widespread concern that even judges are not always well equipped to assess expert evidence, or to act as gatekeepers. Henderson and Seymour found strong support for anecdotal reports that expert witnesses dislike the court process and would prefer not to be involved. Such concerns reflect “long-standing issues with the court process and with lawyers”, they say.

The research, funded by a grant from the 
New Zealand Law Foundation, aimed to look at aspects of the use of expert witnesses in child abuse and neglect hearings, including the use of adversarial examination and the efficacy of witness preparation or training programmes. It arose from concerns that expert witnesses found giving evidence in such cases unpleasant and counter-productive. There were also questions about the reliability of the evidence.

The report says that while criminal and family courts often rely on expert witnesses there can be mistrust of their motives and skills – there is a deep and long-standing suspicion by both lawyers and the judiciary that the experts might misrepresent the facts and overawe the juries, depriving them of their critical faculties.

There are examples in New Zealand and in overseas jurisdictions where unreliable expert witnesses have led to wrongful convictions. There are also persistent anecdotal reports of experts themselves mistrusting the courts so greatly that they refused to give evidence.

Problems with expert evidence cited in the research literature include concerns that flawed evidence is being presented to courts, for example due to deliberate dishonesty, incompetence or bias. There are further concerns that juries, and even judges, are not competent to assess expert evidence and notice its flaws. Additionally, it was felt that jurors may be “overwhelmed by the authority or charisma of the expert”, thus usurping the juries’ function as fact-finders. Such concerns raise questions as to whether the traditional safeguards of the adversarial trial system are sufficient to identify flaws in the evidence and the treatment 
of expert witnesses in the court process, the 
report says.

The research highlights the “essential paradox of expert testimony” where jurors are regularly called upon to evaluate expert evidence but their expertise to do so is limited. The researchers point to the support provided by Doctors for Sexual Abuse Care to a New Zealand Law Commission proposal to abolish juries in sex assault trials given the difficulties juries have in understanding expert evidence.

In New Zealand two tests – utility and risk analysis – have to be met before expert evidence is admitted. This means that for expert evidence to be admitted, it must be so be far removed from a juror’s experience that it becomes useful or necessary to be put before them so they are able to decide an issue. The evidence must also be sufficiently reliable to risk putting it before the jury, meaning it is vetted to ensure there is not too great an error if the jury accepts it without proper consideration.

Potential problems arise where the evidence is complex, technical and lengthy. Henderson told Law News that this tends to harm the defence case more as defendants only rarely call experts. “The burden of making complex methodological flaws apparent on cross-examination falls more heavily on [the defence].”

The report notes there are already limits on using juries in serious fraud trials, given the complexity of evidence. And there are further concerns that juries are not equipped to detect bias amongst expert witnesses. Henderson says it is not always that easy for the defence lawyers to draw out such biases in cross-examination.

The report refers to a 1999 New Zealand study which looked at 312 jurors in 58 criminal trials, of which 19 included expert witnesses. It had revealed that jurors knew little about the court process, finding it confusing. A substantial number found even understanding the evidence of ‘normal’ witnesses difficult, and reported struggling with the volume of information they must absorb from oral testimony. “These pressures may increase any difficulty comprehending expert evidence”.

Studies have shown that jurors find statistical and technical evidence the most difficult to absorb and struggle with terminology like ‘probable’ or ‘consistent with’. They also tend to rely on peripheral factors like the expert’s personal characteristics and qualifications when the evidence is too complex. Jurors may also fall back on their prior understanding of an issue.

There is also concern about a judicial ‘culture of acceptance’ of expert evidence. In some studies in the US it was found that judges were no better than jurors in comprehending expert evidence. However the experience and education of judges can help them overcome common errors.

Another US study suggested that defence counsel could not be relied upon to challenge experts sufficiently and, even where they do, such cross-examination does not necessarily have much impact on the jury’s opinion of the original expert. Furthermore, some critics of the adversarial process argue that it can polarise experts to create a false appearance 
of controversy.

In interviews with expert witnesses the 
New Zealand researchers found that witnesses would like more assistance from lawyers to ensure they were well briefed. They wanted training in courtroom skills and a greater understanding of the adversarial system’s philosophy and the impersonal nature of the cross examiner’s criticisms. The experts generally regarded cross-examination as word-games and trickery. Many felt their evidence was obstructed or misrepresented under cross-examination.

Interviews with lawyers found that there was a strong belief that many juries struggle to comprehend expert evidence. They described this as “a kind of open secret amongst lawyers”. Some lawyers also admitted to struggling with understanding the evidence themselves. There were widespread calls for greater use of pre-trial time to determine the admissibility of expert evidence. There was also criticism about the 
use of  ‘hired guns’ or ‘activist’ expert witnesses.

The researchers say options to improve the use of expert witnesses could include some form of accreditation, and court-imposed codes of ethics. The researchers strongly recommend the provision of information material in courtroom processes for the witnesses.

The researchers also recommend more training for lawyers in the assessment of expert evidence and the need to properly brief experts. Judges should also get extra training, and some specialisation of judges hearing complex expert evidence could be considered. Henderson told Law News that the response to the report had been “thoughtful and interested”, especially from the judiciary.  

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