In 1961 Darryl Beamish, an affable and profoundly deaf 19-year-old, agreed with police that he'd savagely butchered a glamorous Perth heiress in her own bed with a tomahawk and a pair of dressmaking scissors.

Mr Beamish made a series of written confessions, following police interviews that were awash with leading questions. They were the backbone of a case that resulted in a death sentence, later commuted to life in prison.

He was later cleared of the 1959 murder of Jillian Brewer.

There isn't a person alive who hasn't occasionally acted as their own worst enemy.

But making a false confession to murder brings self-sabotage to a terrifying new level — and it's more common than most of us imagine.

Up to a third of wrongful conviction cases involve a false confession. Perth has been home to a string of such cases — and it's given the world's most isolated big city a reputation for miscarriages of justice.

Like that of teenager John Button, who in 1962 confessed to the hit-and-run death of his beloved fiancée Rosemary Anderson. John Button waited nearly 25 years to prove his innocence. ( ABC TV )

"I really thought that if I made a confession it wouldn't be of any good to them, because there was no evidence to back it up," Mr Button recalls.

"I hadn't run Rosemary down, so in order to get away from them I said, 'OK, whatever you say. If you want me to say I did it, I did it.'"

He was exonerated 44 years later.

Or consider Gene Gibson, a cognitively impaired Indigenous man who in 2010 falsely admitted fracturing the skull of a young white boy, a total stranger, for no apparent reason.

First the 21-year-old told police he'd hit the boy with his car. When they looked displeased with that answer, which didn't fit the forensic evidence, he tried again.

"Rock?"

No response.

"Pole?"

His conviction was overturned in April this year.

Or Andrew Mallard, a daydreaming drifter, who explained to police in detail how he thought a suburban shopkeeper might have been bashed to death in broad daylight in 1994, and even drew a picture of the murder weapon.

"If Pamela Lawrence was locking the store up, maybe she came in through the back way, the front door was already locked … Maybe she left the key in the back door and that's why he had easy access, and that's why she didn't hear him until he was … in the store," he recounted to police.

But was this a confession — or a theory?

Coercion, promises and outright lies

Each of these landmark cases, investigated in Earshot's Wrongful series, resulted in an overturned conviction, and the "confession" revealed for what it was: a con.

But how is lying to incriminate oneself even a thing?

As the issue of false confession becomes more widely studied, some clear answers are beginning to emerge.

Coercion by interrogators — both physical and psychological — features in the vast majority of false confessions.

Mr Button, painfully shy and diminutive, was punched in the stomach, denied food and water, and informed casually that his girlfriend, whom police insisted he had struck with his car, had died in casualty.

Mr Mallard, whose conviction was quashed by the High Court in 2006, testified that he was stripped bare by detectives in the course of his interrogation.

A memorial marks the spot on the Broome Highway where Josh Warneke's body was found. ( ABC Kimberley: Ben Collins )

Suspects may even be told outright lies during interrogation, like "your girlfriend told us you did it" or "your fingerprint is on the murder weapon".

The tactic is illegal in Australia, but common nevertheless.

Detectives assured Mr Gibson that a friend had already dobbed him in for the murder of young Josh Warneke.

He was not told that the "witness" recanted the accusation within minutes of having made it, protesting that police had put the words into his mouth.

A classic good cop, bad cop tactic for eliciting a confession may involve an interrogator who appears to empathise with the suspect.

"Of course you were angry at her — it must have been infuriating to be treated like that," is an example Mr Button recalled from his own interrogation.

One very simple technique is simply rejecting the suspect's repeated denials — often for many hours on end — while implying that a confession will guarantee lenient treatment.

Mr Button, distraught and exhausted, fell prey to that strategy, as well, only to find himself arrested for wilful murder — a hanging offence at the time. Listen to the series Susan Maushart explores a series of wrongful imprisonments in Western Australia.

Mr Gibson, a native Pintupi speaker whose grasp of English was severely limited, was led to believe he would get "big time" jail if he entered a not-guilty plea, but only "little time" if he confessed.

Vulnerable people most at risk

People with disabilities, those with substance abuse, Indigenous people, and minors — are all significantly over-represented among the wrongfully convicted.

Mr Beamish was profoundly deaf at a time, the 1960s, when education for hearing-impaired Australians was in the dark ages. While his intelligence was later assessed to be normal, Mr Beamish was at best semi-literate.

"Me Kill Lady Cottesloe", he allegedly scrawled in the sand of the exercise yard while in custody.

At trial, Mr Beamish insisted that he'd written "Me NOT kill lady Cottesloe" — and that he did so in answer to a question from a fellow prisoner. That prisoner later mysteriously vanished.

Mr Beamish spent 15 years in jail, and was finally cleared of the murder in 2005. Darryl Beamish with his wife Barbara in 2011. ( Supplied: West Australian )

Mr Mallard had been recently diagnosed with bipolar disorder and was a heavy cannabis user at the time he "confessed".

And Mr Gibson, with comprehensive cognitive impairments stemming from foetal alcohol syndrome disorder, almost certainly failed to grasp the consequences of his statements to police.

Not surprisingly, questioning minors without a parent present is another risk factor for false confession. Mr Button was never informed that his parents were waiting just outside the interview room.

Mr Beamish too was deliberately isolated from family support during questioning.

Suspects from vulnerable groups are also highly susceptible to suggestion ("Here's how we think you did it") and eager to please authority figures.

"Gratuitous concurrence" is the technical term for a disempowered person's tendency to nod and smile under interrogation — compliant responses which may be uncritically accepted as admissions of guilt by untrained observers.

Does the end justify the means?

Yet none of this explains why securing a conviction too often becomes an end in and of itself.

Some criminal justice experts cite "noble cause corruption" — basically, where police are so convinced of a suspect's guilt they believe the end (a conviction) justifies the means.

One former state attorney-general explained that "achieving closure" was "the whole point of the criminal justice system".

And achieving justice?

"Oh yes, of course. That too," he allowed.

Such notions are simply baked into our "winner-takes-all" adversarial system of justice, argues Bret Christian, author of Presumed Guilty: When Cops Get It Wrong, and Courts Seal the Deal.

Convictions at any cost become a zero-sum game that police, prosecutors and even the judiciary have shown themselves to be all too willing to play to the death.

In Australia, as elsewhere, juries and judges remain notoriously resistant to acquit in cases where the accused has made a confession and then recanted.

With increasing numbers of convictions being overturned, long-overdue reforms are being rolled out to prevent rather than repair the damage.

In Western Australia, tougher disclosure rules now block the withholding of evidence by prosecutors, and an overhaul of police training is underway, with particular emphasis on interviewing vulnerable individuals.

Old-school policing, with its reliance on "copper's instinct" and impatience with evidence-based forensics, is officially (although not always in practice) a thing of the past.

At the same time, new "right to appeal" legislation — recently introduced in South Australia and Tasmania, and currently being prepared in Western Australia — has smoothed the way for appeals based on fresh and compelling evidence.

Now if only humility could be achieved by legislative fiat too.