The words that helped wrongly convict Kathleen Folbigg.

Prosecutor: Are you able to say whether or not Caleb died from a catastrophic asphyxiating event of unknown causes?

Pathologist: I believe that is likely. […]

Prosecutor: In relation to Laura […] her cause of death was consistent with smothering?

Pathologist: Yes.

Prosecutor: Including deliberate smothering?

Pathologist: Yes.

Prosecutor: And that she probably died from an acute catastrophic asphyxiating event of unknown causes?

Pathologist: Yes. – (Transcript pp. 746-48)

The above exchange occurred during the seven-week trial leading to Kathleen Folbigg’s conviction for the deaths of her four infant children (Caleb, Patrick, Sarah and Laura) between 1989 and 1999. During the trial, the word "asphyxia" in its various forms (-ate; -ation; -ating) was used 208 times; "smother" (-ing; -ed) 221 times; and "consistent with" 233 times.

The pathologists and doctors concurred that the absence of external injuries was "consistent with" Caleb dying of a "catastrophic asphyxiating event". This was repeated for each of the four children by each of the doctors, with strangling or smothering likely to be uppermost in the minds of the jurors.

Of course, Folbigg's wrongful conviction had numerous factors. We have no way of knowing why the jury decided as it did.

But there are good reasons for forensic medicine practitioners and advocates to rethink their understanding – and use – of these words.

The semantic journey of asphyxia.

"Asphyxia" first appeared in print in 1699 defined as "without any Pulse, or sign of Life". Predictably, this meaning "stoppage of pulse" then sprouted the meaning "stoppage of respiration" – a lack of breath is a salient sign of lifelessness.

Subsequently, the path has been rocky, and it is now understood variously by forensic doctors around the world. What is agreed, however, is that "asphyxia" is not a diagnosis; it is not a condition that can be pointed at or diagnosed.

As far as lay understandings go, things get murkier. Modern dictionaries list many senses but privilege "respiratory failure", with "suffocation" usually given as a synonym; this in turn is defined as the interruption of breathing, including some means by which it’s brought about (for example, smothering, throttling).

The Urban Dictionary’s definition for "asphyxiation" is "death by strangulation; ergo blockage in air passage". This dictionary has its problems, but like other collaboratively constructed dictionaries, it is useful for tracking contemporary social meanings of expressions not yet in more mainstream dictionaries.

More murkiness.

In the trial, confused senses of "asphyxia" were combined with the misleading phrase "consistent with". As used by experts, this is synonymous with "may or may not mean".

Research shows, however, that people without expert knowledge hear the phrase as strong confirmation of the proposed connection.

In the 1998 Canadian inquiry into the (wrongful) conviction of Canadian man Guy Paul Morin, Commissioner Kaufman was scathing in his criticism of the use of "consistent with". He regarded it as demonstrably misleading language, variably being used to mean:

‘could have come, or cannot be excluded as coming, from the accused’; ‘not inconsistent with’; ‘more than a possibility but less than a probability’; ‘perfect or near identity of two items’.

The historical thesaurus of the Oxford English Dictionary suggests this last sense "perfect or near identity of two items" has been around since the 1600s. Clearly, we can't assume people today would automatically understand "consistent with" as simply a way of saying what is proposed is possible.

Bad meanings drive out good.

The meanings we carry around in our heads seem so natural we fail to realise other people can have quite different understandings.

As linguist Nick Enfield describes, we hypothesise what others mean by the words they use. And the more unusual a word is, the more its meanings will vary because we aren't given the same opportunities to refine our hypotheses.

For example, what part of the foot do you understand as the "instep" – the upper surface between toes and ankle, the underneath part, or perhaps both the top and underneath? All three meanings are out there, and different dictionaries favour different ones.

Does this really matter? In a highly circumstantial murder trial, it does.

Words are far more likely to take on negative overtones than favourable ones. The linguistic evidence is compelling – negative senses come to dominate and eventually quash all other senses. This transformation has a name: Gresham’s Law of Semantic Change.

It comes as no surprise that crowdsourced online dictionaries show the homicidal senses of "asphyxia" (and its derived forms) as winning out.

Asphyxia permeated Kathleen Folbigg's trial.

Importantly, it was agreed by all involved none of the babies showed any injuries. (Two pinpoint scratches on Sarah’s lower lip were agreed to be of no significance).

As the prosecutor said:

All they [the doctors] can say is that there was some form of obstruction that caused oxygen not to be able to get into the lungs and that’s what caused these babies to die […] all they can say is that it was induced asphyxiation from an external cause […]“ (Transcript p. 66)_

It was repeatedly asserted the presence of no injuries in any of the Folbigg children "was consistent with the occurrence of an acute catastrophic asphyxiating event" or "smothering". This was probably heard by the jury as indicating no injuries meant an "asphyxial event" had occurred – in other words, the children had been strangled or smothered.

There was also repeated reference to the absence of natural explanations for four sudden and unexplained deaths in one family – with the unstated inference that the only reasonable explanation was homicide. Known as Meadows Law, this inference stalked Kathleen Folbigg's trial and her subsequent appeals relentlessly. Meadows Law falls at the first hurdle: how likely is it there would be four murders – where there are no injuries – masquerading as natural deaths?

In his sentencing remarks, the judge stated:

No (expert) witness was prepared to say that the signs pointed only to smothering but the medical evidence generally was that the result of each event was consistent with having been caused by acute asphyxiation. The jury accepted that evidence.

That summary encompasses the following linguistic storm: the doctors might say they thought the prosecutor was talking about asphyxia as meaning hypoxia/anoxia (low oxygen levels) due to any one of a myriad of causes.

The prosecutor believed he was asking whether, and the doctors were telling him that, the babies died from induced airways obstruction from external causes. And the jury thought they were being told the babies were smothered, or even strangled.

All of this is medically incoherent and incapable of establishing anything of significance – but probably had a powerful effect on the jury.

'The wisdom of the crowd'.

Since its first appearance in English in the 1600s, the term "asphyxia" has caused confusion.

In forensic pathology, it encompasses a number of concepts and is used variously by pathologists – and these uses are out of alignment with common lay usage. Combined with different understandings of "consistent with", this confusion was very much to Folbigg's disadvantage.

The jury system relies on "the wisdom of the crowd". Forensic doctors, advocates and judges must recognise that, despite what they think and dictionaries say, the crowd can understand words very differently, and this can have consequences.

Kate Burridge, Professor of Linguistics, Monash University and Stephen Cordner, Senior Consultant/Professor Emeritus, Dept of Forensic Medicine, Monash University, Victorian Institute of Forensic Medicine.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Feature image: AAP.