TRUE CRIME is a sleazy, uneasy genre. Accounts of murder, in newspapers and in books, seem to prey on suffering and to play to their readers' darkest fantasies.

In the notorious Road Hill House murder of 1860, the subject of my own true-crime book, a three-year-old boy was abducted from his cot, stabbed, and pushed down a privy in the grounds of a country house. The press reported vividly on the murder and speculated wildly on which member of the child's household had killed him, in articles that coupled visceral thrills with the high-minded seriousness of detection and analysis. This is part of the fascination of true-crime writing: it is morally precarious, as if infused by the dangers it describes.

The templates for crime writing - real and fictional - were laid down in the mid-19th century. Thanks to the repeal of the stamp tax in 1855, newspapers had taken root all over England by 1860, most of them producing astonishingly thorough and candid crime reports. The lavish press coverage of the Road Hill House case inspired other writers. Barristers and physicians published their solutions in pamphlets, baronets and vicars penned letters to the papers. For enigma and intrigue, this crime outstripped fiction. “If the late Edgar Poe had sat down to invent a tale of mystery,” noted an editorial in The Times, “he could not have imagined anything more strange and perplexing.” The story worked its way into Charles Dickens's last book, The Mystery of Edwin Drood, and into Wilkie Collins's The Moonstone, the original English detective novel.

Those who reported on the crime were eager to give a moral dimension to their curiosity: “A deed that sends a shudder through every English home,” claimed the Bath Chronicle, “acquires a social importance which justifies any amount of attention to the subject.” The paper noted that women showed an intense interest: “It is the mothers of England who write most earnestly ... to the conductors of the journals, and almost clamour for the most unsparing search and the most untiring test.”

Victorian ladies had an appetite for true tales of murder. They were enthusiastic visitors to Madame Tussaud's new Chamber of Horrors and keen spectators at sensational court cases. This tendency was satirised in contemporary novels: “I dearly like a murder,” says Mrs Mush in Julia Kavanagh's Sybil's Second Love (1867). “Of course I do not wish for murders, but when there is one, why I like it.” At the inquest that followed the Road Hill murder, a bystander remarked: “Women had crowded into the room to hear how a throat had been cut, and they held young children in their arms to gaze upon the bloody relic.” When the contents of the house were put up for auction, days after the victim's family had abandoned the property, the place was besieged with young women in search of bloodstains and morbid souvenirs. These were hardly the domestic angels of Victorian fantasy.

The Road Hill case was compelling because it exposed the lies, adultery, sickness and madness that had festered in an apparently respectable home. The investigation of the murder threw up scores of details of the family's domestic habits, which acted as a counterpoint to their disturbing and impenetrable inner lives: we know when the milk was scalded for breakfast in June 1860, how the lawn was cut, what the nursemaid ate for supper and the fabric of the daughters' nightdresses. The police files reveal the nitty-gritty of the investigation, too: Jack Whicher, the detective sent to Wiltshire to solve the mystery, recorded his day-to-day operations in reports and expenses claims.

In the most effective true-crime books, extreme emotion is combined with humdrum detail. In Cold Blood by Truman Capote gives us the minutiae of the lives of two shiftless, violent ex-convicts in 1950s America. Brian Masters' Killing for Company and Gordon Burn's Somebody's Husband, Somebody's Son reconstruct the ordinary worlds of serial killers in 1970s England. We are immersed in the poorest reaches of early-19th-century London in Sarah Wise's The Italian Boy and in the badlands of late-20th-century west Baltimore in David Simon's Homicide.

The first book on the Road Hill murder was published within a year - it was perhaps the first book-length account of any single murder. In The Great Crime of 1860 Joseph Stapleton observed that the theories about the case were as interesting as the crime itself. Who in the Road Hill household was the public inclined to blame? The scheming servant? The deranged adolescent? The sex-crazed patriarch?

In each of the suspicions about the identity of the murderer Stapleton found “striking and instructive comments on the condition, habits, and feelings of society as it exists amongst us. Every one of them has its psychological lesson.” A true-crime story may pander to our darker instincts, but it lights up inner worlds as well, our own and those of others: it can show us the killer and also the detective, the victims and also the voyeurs.

The Suspicions of Mr Whicher: or the Murder at Road Hill House by Kate Summerscale
Bloomsbury, £11.99; 384pp Buy the book

The Times Cheltenham Literature Festival: Kate Summerscale discusses The Suspicions of Mr Whicher: October 10, 2pm
cheltenhamfestivals.com

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