Like Lindy Chamberlain before her, Erin Patterson has become the woman everyone loves to hate.

It’s not difficult to see why. A woman serves up a beef Wellington lunch, and three of her in-laws end up dead from suspected death cap mushroom poisoning. Patterson claims she also ate a portion. After the guests had left, she evidently binged on the remaining slices of the orange cake that they had for dessert, and felt so full she went to the toilet and vomited.

People called Lindy Chamberlain evil. Dr Chris Webster, who treated Erin Patterson and the other victims at Leongatha Hospital, called Patterson evil. He said when she told him she had got the mushrooms from “Woolworths”, he felt she was “guilty”.

The defence, however, argued that Patterson had accidentally used death cap mushrooms, which are notoriously difficult to identify.

In the media glare, nuance gets lost. From my experience covering the Andrew Fitzherbert case, the first Australian trial based on DNA evidence, I know that things are rarely as simple as they first appear. Between 2007 and 2011, I wrote several articles about the Fitzherbert case, including for the _Crime Magazine_, _Online Opinion_ and The Courier-Mail.

In August 1999, Fitzherbert, a Brisbane palmist, was convicted of the 1998 murder of Brisbane veterinarian Kathleen Marshall, a woman dubbed “Catwoman” because she was president of the Cat Protection Society. At the time of her murder, she was caring for about 17 cats while seeking homes for them.

There were no witnesses, no motive established, and no murder weapon found.

In the media and public mind, Fitzherbert was quickly branded as an eccentric, ruthless killer. His interest in palmistry and alternative lifestyles only fed the perception. There were no prominent voices suggesting he might be innocent.

Discrepancies in the case have puzzled observers for years, including such basic information as the time of death. A Health Department scientist told the court that Marshall probably died between 9pm on Thursday, 27 February 1998, and 3pm the next day. On this basis, the prosecution argued the murder likely occurred on Thursday night. But it is much more likely the murder took place sometime on Friday night. Four witnesses, including the local newsagent and pharmacist, testified they saw Marshall late on Friday afternoon.

The cornerstone of the defence was DNA evidence (analysis of five drops of blood) given by Ken Cox, a forensic biologist from the John Tonge Centre ‒ a laboratory with a history of errors. It has come under continued scrutiny for slack procedures and mishandling of evidence, raising further questions about the reliability of the DNA results used to convict Fitzherbert.

One key figure who raised doubts and challenged Cox’s interpretations was the late Professor Barry Boettcher, a DNA expert who was influential in uncovering problems with evidence in the Lindy Chamberlain case.

Ted Duhs’s 2012 study of miscarriages of justices in Queensland _Crucial Errors in Murder Investigations_ (Boolarong Press) draws on many cases, including Fitzherbert’s and Chamberlain’s ‒ and serves as a timely warning. A criminal trial is not a search for the truth: our legal system is based on the principle of proving guilt “beyond reasonable doubt”. But as Duhs shows, doubts often emerge years later.

The jury in Patterson’s trial faced an immensely difficult task, weighing complex forensic evidence and testimony. They took 6½ days of deliberation, which suggests that one or more jurors had a reasonable doubt about Patterson’s guilt. Their verdict deserves respect as a cornerstone of our justice system. Yet, like many such cases, the public — and even jurors themselves — may wrestle with doubt and uncertainty long after the trial ends.

The jury in Fitzherbert’s trial also weighed the evidence carefully and delivered their verdict. However, years later, I received a handwritten letter from one of those jurors expressing serious doubts about the verdict. He told me they had been heavily influenced by the expert witness Ken Cox and in hindsight, he believed the jury may have got it wrong.

What troubles me is how much of the public discussion has been shaped by emotion. “She’s a liar.” “She’s crazy.” “She’s full of hate.” Some point to Patterson’s supposed loathing of her in-laws. From what I read, she had a closer relationship with them than many estranged or divorced couples might maintain.

The details people fixate on — Patterson wearing white pants — remind me of the minutiae that obsessed the public during the Chamberlain case. Why would she wear white pants if she was experiencing diarrhoea, people ask? And why did she show no emotion? As if what she wore or her lack of concern could somehow point to her guilt. Chamberlain’s baby, Azaria, went missing at Uluru, and a nation decided her demeanour made her guilty. Weren’t both Chamberlain and Patterson in shock?

Yes, Patterson told some lies after the tragedy — perhaps out of panic, shock or confusion — but such reactions are hardly unusual in the aftermath of trauma. Lies by themselves are not strong evidence of guilt.

We seem drawn to judging women particularly harshly: mothers, wives, ex-wives, sisters-in-law. I find myself wondering if Patterson isn’t just the latest in a long line of women tried in the court of public opinion.

Above all, this is a story of loss ‒ three people dead, their families shattered, and a surviving family member struggling with grief. And let’s not forget Patterson’s children, family and friends caught up in this painful saga. The human pain on all sides must not be forgotten.

I don’t know if she’s guilty or innocent. (Only Patterson knows the truth). But I know the danger of certainty. That’s something I learned years ago, while investigating the Fitzherbert case.

The views expressed in this article may or may not reflect those of Pearls and Irritations.