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The conviction of Robert Farquharson for the murder of his three sons on Father鈥檚 Day 2005聽聽in the media, with doubts raised about the reliability of prosecution鈥檚 medical, traffic reconstruction and sinking vehicle evidence.

This case has echoes of聽,听听补苍诲听. Their murder convictions were overturned when scientific and medical testimony from their trials was eventually found to be unreliable.

The handling of expert opinion evidence by Australian courts is in a crisis. Curiously, our courts appear oblivious. They use forensic science evidence without regard for the best scientific advice.

Australian courts ignore criteria recommended by peak scientific organisations such as the聽听补苍诲听聽(AAS). The chief executive of the AAS, Anna-Maria Arabia, has warned that聽聽鈥渏unk science鈥�. Why is this happening and what can we do?

Unlike most witnesses who can only testify as to facts, experts are allowed to express opinions based on 鈥溾�� that would otherwise be unavailable to the court. Prosecutions frequently rely on expert evidence such as DNA profiles, fingerprint comparisons and post-mortem reports.

Problematically, courts fail to insist on formal validation of the experts鈥� methods before their opinions are admitted. In 2009 the聽, apart from DNA, no forensic method has been rigorously shown to [鈥�] consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.

The academy expressed concerns about the accuracy of expert comparisons of fingerprints, ballistics, hairs, handwriting, bite marks, explosives, paints and blood stains.

Scientists have been working hard to enhance forensic sciences in the aftermath of the report. While there have been validation studies and practical improvements in some areas,听聽have typically remained critical in their evaluations.

For example, fingerprint examiners聽聽but not infallible, as was claimed historically. Their error rate is roughly 1 in 400.

Other comparison procedures fared less well. For example, despite formal qualifications in dentistry and forensic experience,听聽a bite mark on human skin with specific teeth. Indeed, they can鈥檛 even determine whether marks on skin聽are聽bite marks.

Bad science in the courtroom

Australian courts don鈥檛 have rules, procedures and personnel that can effectively regulate the admission of these types of evidence.

Forensic scientists can implicate defendants without reference to validation studies and without appropriate caveats. Courts are often shielded from error rates and scientific criticism. Little account is taken of the risk evidence is biased by examiners鈥� exposure to information implicating the suspect, and examiners鈥� close relations with prosecutors.

Australian courts have also ignored聽听补苍诲听聽that we need to tighten the rules for what evidence is admitted in court.

Rules require expert opinion to be substantially based on 鈥渟pecialised knowledge鈥�, but this doesn鈥檛 involve the reliability of that knowledge.

Australian courts tend to rely on proxies for specialised knowledge. These can be general qualifications, job titles, experience, previous appearances in court and the plausibility of the expert鈥檚 interpretation.

No one in court 鈥� neither prosecutors, expert witnesses, nor trial and appellate judges 鈥� addresses the all-important questions: can the expert do it? How well? And how do we know? As a consequence, 鈥渏unk science鈥� is routinely admitted, leading to incurable unfairness and even wrongful convictions.

Defence counsel are also at fault. Australia鈥檚 leading advocates are rarely effective in cross-examining forensic scientists about the validity and accuracy of their opinions.

American legal scholar John Henry Wigmore said cross examination is 鈥渢he greatest legal engine ever invented for the discovery of truth鈥�. But it consistently fails, as have聽, such as opposing witnesses and judicial directions.

Expert evidence of dubious reliability is regularly admitted and left to the jury to somehow evaluate.

Ignorance isn鈥檛 an excuse

Perhaps the criminal justice system鈥檚 scientific ignorance shouldn鈥檛 be surprising. This ignorance is the very reason we need expert evidence.

But lawyers and judges can become complacent toward their critical abilities and the effectiveness of traditional legal rules, procedures and safeguards. (This complacency contributed to the failure of the 2019 inquiry to correct聽.)

The very reason for holding a trial is that we don鈥檛 know if the defendant is guilty. But this unknown and the finality of a jury verdict means we don鈥檛 tend to get meaningful feedback on the system鈥檚 effectiveness (or lack thereof).

Evidence-based reform is urgently needed. We should impose聽an explicit reliability standard聽on all expert opinion evidence. Courts need to understand the limitations of forensic science and medicine evidence. Their proud legal traditions should not insulate them from the chorus of advice from peak scientific bodies.

The federal government should create an independent multidisciplinary panel聽聽on controversial subjects such as CCTV and voice identification, or whether there are reliable means of identifying abusive infant head trauma.

Finally, Australian governments should also establish an independent Criminal Cases Review Commission to uncover and refer potential wrongful convictions聽.

Such a body, operating outside the traditional adversarial system, may help persuade complacent criminal courts that seemingly damning 鈥渆xpert鈥� evidence should not always be taken at face value.

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Professor David Hamer is Professor of Evidence Law in the Sydney Law School at the University of Sydney. This story, co-authored with Gary Edmond, Professor of Law at UNSW Sydney, was first published on聽: 鈥楯unk science鈥� is being used in Australian courtrooms, and wrongful convictions are at聽stake.