In May 2004, a 19-year-old Perth schoolgirl named Rebecca Ryle was strangled in a park, just 50 metres from her home.

She was last seen walking off with 20-year-old James Duggan, an unemployed high school dropout who filled his days smoking weed and playing XBox. They had met earlier that night at a popular northern suburbs tavern.

Ryle was a shy, level-headed and kind young woman, well-liked by her class-mates and teachers. Born in England to British parents, Ryle had migrated to Perth with her family – her father, a technician in the Royal Navy, looking for a better life in the expanding heavy industries of Western Australia.

Her body was found in the grounds of Mindarie Primary School, practically in view of her front door. Her pants and underwear had been removed, but there was no sign of sexual assault.

It didn’t take long for police to track down Duggan and arrest him, and for him to admit strangling Ryle. In his initial police interview, though, he could not explain why. He never would provide an adequate explanation of the night’s events.

This lurid but apparently motiveless crime touched many in Perth’s northern suburbs. Among them was Martin McKenzie-Murray, also the child of British migrants living in the sandy expanses of Perth’s north. On a whim, McKenzie-Murray decided to attend Rebecca’s funeral, joining hundreds who turned out for the occasion, to pay tribute and attest their grief.

Years later, a successful journalist on the east coast, McKenzie-Murray found himself fascinated by the crime and what it implied about Australian adolescence. Contacting Rebecca Ryle’s parents, Fran and Marie, he struck up a dialogue, and eventually they gave him their blessing to write a book.

The result is A Murder Without Motive: The Killing of Rebecca Ryle (Scribe), one of the more unusual examples in recent years of the ‘true crime’ genre, that reliable and rough-hewn sector of the local publishing market. Often disparaged for its steady sales and sensationalist approach to lurid crime, the literary snobbery is barely deserved – the genre has been the home of some of Australia’s best writers in recent decades, from Helen Garner to Anna Krien.

McKenzie-Murray is best known for his journalism at The Saturday Paper. There, as the newspaper’s chief correspondent, he has been a clear-eyed investigator of some of the darker corners of Australian social affairs. McKenzie-Murray has written about child abuse, domestic violence and suicide, as well as the more prosaic topics of federal politics and economics, approaching these difficult subjects with admirable honesty. In A Murder Without Motive, McKenzie-Murray takes an expansive view of human violence, ranging through memoir into essay, from sociology to psychology and criminal justice, asking what the murder tells us about Australia in the twenty-first century.

The answers are not comforting, especially for an Australian mainstream that remains complacent in its suburban verities. McKenzie-Murray is particularly interested in teenage cultures of masculinity, which he writes about with unabashed disdain. It is a tale of adolescence, full of anomie, longing and violence.

What develops is in many respects a sort of dystopian Australian roman a clef, in which McKenzie-Murray riffs off the events surrounding Ryle’s murder to explore the suburban vernacular of beers, bongs, footy and fights. Throughout – for the most part – he maintains a rare sensitivity to his subject matter, accompanied by a sensitive, mannered and at times even literary style.

In chapter one, for instance, McKenzie-Murray describes a brawl at a teenage party he attended, in which an acquaintance named Brandon was bashed.

As he approached, I warned him that being there was a very, very bad idea. But it was too late; he never made it across the front lawn. He was set upon by many, his face smashed. As he retreated to the road, he fell and was stomped. His swollen mouth called for clemency, but you could barely hear it from the primal shouts of his attackers. I remember standing on the lawn, in more or less the same spot in which I had warned him, and watching as a girl brought her stiletto down on his body …

A police siren quiets the mob for a moment, but, tellingly, it turns out the police were attending a different disturbance down the street. Brandon attempts to hide inside the house opposite.

As the mob moved towards him, Brandon made a final, desperate decision. Nearly 20 years later, I’m still stunned by my memory of what happened: he sought refuge by crashing through the front window. And that was the end of our Black and White Ball.

‘None of this happened in slums or public housing,’ McKenzie-Murray points out. ‘This was the middle class. But livid visions of masculinity played themselves out vigorously.’ It is these ‘livid visions’ that McKenzie-Murray plunges into, in an attempt to tease out the tragic strands of Rebecca’s fate.

@feed_the_chooks & Gideon Haigh in conversation at the @wheelercentre tonight for @KYD_journal's First Book Club pic.twitter.com/lyC5w1naRo

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At the heart of the riddle is Duggan’s culpability. He was never able to explain why he strangled Ryle. Across many interviews and an eventual trial, Duggan was able to offer no convincing explanation for his motive, or even his mental state, at the crucial moment he strangled his victim. Psychological and psychiatric assessments were unhelpful. Police, prosecutors and eventually McKenzie-Murray himself all offer plausible scenarios, but the hard truth is we will never truly know. In the end, the judge presiding over the case would declare, ‘I simply do not know why you did what you did, and to assign a motive to you is simply to speculate.’

McKenzie-Murray also explores the normative no-man’s-land of Western Australia’s legal system, which has a special category of murder that does not require premeditation. He unpicks the various ways in which the justice system failed the family of the victim, particularly in a trial where the many lacunae of evidence made proving the first-degree nature of the murder beyond reasonable doubt so difficult.

In truth, though, the centrepiece of the book is not the crime and its punishment, which McKenzie-Murray dutifully describes. Rather, the book’s real achievement is the author’s remarkably sensitive exploration of the Ryle family, particularly Rebecca Ryle’s parents, Fran and Marie, and the ‘ferocity’ of their enduring grief.

‘In our minds,’ McKenzie-Murray writes towards the end of the book, ‘we effortlessly solve open murders by apportioning blame to the victim.’ But in doing so, he argues, ‘we are injuring our imaginations – the lifeblood of sympathy – and misapprehending the nature of violence.’

A Murder Without Motive is available now through Readings.