In a courtroom drama, the moment the hero lawyer stands to begin their cross-examination, the room falls silent with expectation.

Fixing their opponent with a steely gaze, they quietly set about dismembering the testimony, character and credibility of someone whose evidence just minutes earlier seemed unassailable. In a flourish, the case is turned on its head.

Actual trials, I hate to report, are less dramatic and rarely as satisfying. But the mechanism is true to life.

Justice and science are a difficult mix.Credit: Matt Absalom-Wong

Cross-examination is said in legal circles to be “the greatest legal engine ever invented for the discovery of truth”. In contested cases, courts rely heavily on a barrister’s ability to test character, tease out facts and unveil falsehoods.

Ken Crispin was just such a barrister, then a director of public prosecutions, then a judge in the ACT. And as a judge, in 2001, he wrote an extraordinary, prescient judgment in a trial over shaken baby syndrome which eviscerated the prosecution evidence. The scientific “proof” of the syndrome, Crispin wrote, was based largely on anecdote, theory and unreliable confessions.

I interviewed him for a forthcoming bonus episode of my podcast, Diagnosing Murder, and our conversation turned to how difficult it was even for a whip-smart practitioner such as himself to properly cross-examine scientists.

Lindy Chamberlain was convicted over the death of her baby, Azaria, on the basis of seven pieces of scientific evidence. Six of them were wrong.Credit: Michael Raynor

As a barrister, Crispin appeared in the 1986 royal commission investigating the wrongful conviction of Lindy Chamberlain. He wrote a book about it and decades later is still outraged at the forensic chicanery involved in her prosecution. There were major errors in six out of seven pieces of scientific evidence used against her. Proving it, though, wasn’t easy.

“We subpoenaed one bundle of documents from one witness and the first page consisted of a series of statements in point form and the points consisted in part of English words and in part of symbols,” he tells me.

“It took me 12 hours with a professor of immunochemistry to work my way through the document and understand exactly what the witness was saying and what might be wrong with it.”

“[After that], in almost any case in which expert evidence was to be given, I would try to persuade my instructing solicitors to engage an independent expert who could advise me, not just the court, so that I’d know what questions to ask,” Crispin says.

That costs money, which many defendants can’t afford. But even if they can, the challenge remains to convey that information to a judge and jury.

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© The Sydney Morning Herald