Devil's advocate: Sophie Hannah has as much sympathy for her villainous characters as her heroes

(DAVID SANDISON)

Sophie Hannah has been trying to invent a new kind of novel. She calls it, with tongue placed firmly in cheek, "non-judgmental" crime fiction. "Everybody, from the hero detective to the worst baddie, is doing their very best given the situation," she explains. "The crimes in my books are committed by people who can't keep it together any more. They do something to express their own pain, and that has a terrible effect on somebody else." Her new thriller, A Room Swept White, for example, revolves around three women accused of killing their newborn babies.

This experiment with a liberal murder mystery might sound strange, but Hannah isn't your typical crime novelist. Her baroquely plotted psychological thrillers have sold more than half a million copies, but she began her career far from the bestseller lists, in the world of poetry. She published five well-received collections of tartly funny and tautly constructed light verse before Pessimism for Beginners was nominated for the prestigious TS Eliot Prize for verse in 2007. It was a watershed moment, although not perhaps in the expected way. Instead of building on the acclaim, Hannah chose this moment to begin her life of crime.

This literary duality turns out to be characteristic of Hannah. We meet in Cambridge, where she and her family have just relocated after a decade spent in rural Yorkshire. (The move is a homecoming of sorts: born and raised in Manchester, Hannah fell in love with Cambridge during a two-year stint as Fellow Commoner in Creative Arts at Trinity College.) Hannah is that rarest of authors: one happy to admit that her work is autobiographical. "Everything is personal – the poems and the crime novels. I have never been involved in any murders, but there are strong autobiographical elements in each." On the surface she is chatty, amusing and optimistic – the sort of person the cliché "bubbly" was coined for. "I am actually incredibly contented and jolly," she says. "But, and I have no idea why this is, I have a really strong empathy with all kinds of warped and destructive modes of thinking. I don't know why, but those things co-exist."

Similar tensions co-existed in her Manchester upbringing. The eldest daughter of devoted parents, Hannah had a happy childhood, but one she also describes as solitary and restless. She found an antidote to loneliness in her imagination. "I would make up whole narratives about complicated relationships. I remember I had seven or eight Sindy dolls and the machinations that went on were just unbelievable."

If this embryonic version of her crime fiction liberated her as a child, teen rebellion continued the process. "My home was so safe and secure. I deliberately sought out dangerous boyfriends because I was so bored by the nurturing of my parents." Her bad boys included ex-prisoners, drug addicts and a pseudo-Hell's Angel who introduced himself by saying that two previous girlfriends had died on the back of his bike. "I still let him drive me around, having several near-death experiences." These days, Hannah reserves her darkest impulses for her fiction.

Although some people seem baffled by her transformation from poet to crime writer, Hannah argues that the two have much in common. "Both have a massive preoccupation with structure. In a poem, every word has to be in the right relation to every other word. In a crime novel, if you are going to have a big revelation in chapter 30, you have to plant the information in chapters three and 11." One fundamental difference, of course, is earning potential. Hannah insists that she writes thrillers for love not money, adding that most of her peers earn less than £10,000 a year. Nevertheless, signs of her own increasing success are everywhere, not least in her new five-storey house – from its penthouse study to its basement sauna. ("It was installed by the previous owner," she explains hastily.)

Hannah may be taking her place among the upper echelons of British crime writers, but she isn't entirely comfortable just yet. A new five-book contract inspired nerves and joy in equal measure. "It was the biggest deal I had done in my career. I felt that, instead of being this person writing in a little room, business was being done. Things moved up a gear. That was great, but also a little bit scary. I thought, 'Who am I to deserve this?'"

Hannah harnessed this ambivalence when creating Fliss Benson, the lead character of A Room Swept White. A junior researcher at a TV production company, Fliss is suddenly promoted, in order to complete a hotly anticipated documentary about three women wrongly accused of killing their babies. One

of the women is murdered, and the only clue is a card with 16 numbers printed on it. When Fliss is sent an identical card, she finds herself lost in a labyrinthine mystery.

The subject of cot deaths, or sudden infant death syndrome, had interested Hannah ever since Sally Clark was wrongly convicted in 1999 for killing two of her sons. Hannah was especially struck by Sir Roy Meadow's claim that the odds of more than one cot death happening in the same family were 73 million to one. "I said to my husband, 'That doesn't sound right.' But on the strength of that statistic, [Clark] was convicted." A Room Swept White attempts to confront the uncertainty that inevitably surrounds cot deaths. Hannah became especially intrigued that, as public opinion fluctuated, the same facts that had once been used to demonise accused mothers were now used to sanctify them. "It really struck me how sides were created. You were either with the doctors or with the mothers."

As the two factions became increasingly polarised, Hannah wondered whether the expert medical witnesses hadn't also been treated unfairly. She cites the judge at Angela Cannings' appeal in 2003, who recommended that in cases where the only evidence of murder is disputed medical evidence, such a case should not go to criminal trial. The problem, Hannah explains, is that most instances where a mother actually kills her child are not witnessed. "Nobody smothers a baby in the middle of the street with the postman walking past," she says. "I began to wonder if good doctors trying to do their best were being slandered. And what if some guilty mothers were being defended along with the innocent? If someone was minded to smother a baby, I would have thought now would have been a great time," she says.

"I grew up thinking the world was made up of goodies and baddies. But nobody is the baddie in their own head. In a case like this – where doctors are trying to protect children and mothers are either innocent or so desperate that they smother their own kids – an adversarial model seemed particularly inappropriate. Each side should have as much understanding and empathy for the other side as possible."

Her equanimity has helped Hannah deal with everything from moving house to bad reviews. For the present, however, her future looks assured. Her work is admired and popular, and looks set to become more popular still: her crime novels are being adapted for a possible television series later this year.

Perhaps this explains her rosy view of life, offered just before her children drag her off for tea. "A character in my last book said, 'Everyone fails eventually.' It's great that thousands of people are reading my books, but what really matters is that I'm writing novels which mean a lot to me." And just when I think Hannah's dark side has been defeated by the light, she has to go and ruin it. "Of course, the irony is that I have to go over them 17 times before they are published. There's no suspense," she laughs. "By that stage, they are the very last books I want to read!"

The extract

A Room Swept White, By Sophie Hannah Hodder £12.99

'... "You're worried about having a once-convicted child murderer in your house," she says. "I understand ..."

"Why do you want to meet me?"

"I'll answer that question, and any others you might have, face to face. Does that sound fair?"

I hear myself say, "Okay"...

That's when it hits me: this is real, and I'm scared'