"I constantly think about how people are reading and how they are managing their time, so I tailor my books to fit. Each chapter used to be 20 pages but now it's 10 pages; the books are still as long, just presented in shorter increments like scenes in a movie, so you have an obvious little stopping point."
In that case let's take advantage of just such a point and disembark, briefly, to talk about the woman behind the work. Having said that, the physical and personal similarities between creator and creation (they are both blond, petite, clever and ride Harley-Davidsons) go beyond the merely striking, although Cornwell point-blank rejects close comparisons.
Her own flinty reputation precedes her; cropped hair, ice-chip blue eyes set in a lean face, a watchful expression and the coiled-up, fight-or-flight air of a lynx about to spring.
She famously doesn't suffer fools, owns a home bristling with firearms and security sensors and is the sort of stickler who installed a forensic lab in her own house so she could carry out much of her fastidious research in-house. Pro-gun ownership but also pro-civil rights and anti-capital punishment, it's impossible to pigeonhole her politically.
"A lot of people think I'm Republican, others think I'm a Democrat, but I vote for the person running for a certain post and I scrutinise what their policies are going to do for civil rights," she says. "I don't believe any politician could or should ever take away the American people's right to bear arms, but I refuse to vote for any party that interferes in my personal choices and tries to tell me who to be in love with or which god I should pray to."
A former journalist, Cornwell's own life story is beset with almost as many twists as one of her byzantine plotlines. Her father walked out on the family when she was 5. She held his leg and begged him not to go, but even many years later, on his death bed, he rejected her; as his children stood round his bed, he mouthed "I love you" to her brother but wrote a single question to his daughter: "How's work going?"
After her mother fell ill with clinical depression, the siblings were taken into care and placed with what turned out to be abusive foster parents. Cornwell suffered from anorexia in adolescence and, later, mental health issues of her own. She married in her 20s, but after she divorced her husband, discovered (belatedly) she was a lesbian; at one point an FBI agent instigated a shoot-out, claiming Cornwell had stolen his wife.
Now married for the past three years to Harvard neuroscientist Staci Gruber, Cornwell lives in Boston. Last year she was awarded $50 million by a court against a financial management company she had hired to look after her money and which, the court found, had significantly depleted her fortune. Yet throughout all this, Cornwell kept on writing. The identity of her heroine was forged during the six years she spent working in a chief medical examiner's office in Virginia, when she saw innumerable autopsies being carried out.
"I'm still a journalist at heart," she says. "I need to see, hear, smell and feel something so I can convey the sensations to my reader. If I want to write about a dangerous new firearm as I do in Flesh And Blood, I go see an expert who shows me how to use it and shows me the damage it can do. I've never had any interest in scuba diving, but because in this book Scarpetta dives off a boat and has a scene 30m under water, I had to do it, too."
When I ask (not entirely) ingenuously whether she couldn't have just got Scarpetta to snorkel instead - after all, she's in charge - Cornwell doesn't so much as crack a smile. "No," she says dismissively. "Scarpetta wouldn't snorkel. To some extent she has changed me in that I have learned lots of skills, like helicopter flying, in order to write about them. My challenge is to stay passionate and vital so I can write great stories that challenge and entertain."
The interplay between author and character is always an interesting one; the way Cornwell tells it, there's a "very strange counterpoint" at the heart of her writing.
"I write about crime, and my books are about the science of death - but also, and much more so, about the art of life," she says. "When I sit down at my desk to write Scarpetta I step through the looking glass and into her shoes. It's my job to endure if she's having a lousy day. I present her with a crime and make her life a misery by withholding information that I possess, but which she has to discover, painstakingly, over the course of the book."
And afterwards, when she stands up and leaves her desk, what then? Does the presence of Scarpetta hover by her shoulder? "I don't have an identity crisis," says Cornwell, crisply. "I live a rich, fulfilled life with Staci and our english bulldog, Tram. We take long walks together, just being in the moment, feeling the fresh air, sometimes talking, sometimes not."
But then she admits that as she walks, she allows Scarpetta's problems and conundrums to filter through her subconscious and that by some mystery of the human mind, things somehow resolve themselves.
When her first book, Postmortem, appeared in 1990, the backroom nature of forensics was not on the public radar, making Cornwell and, indeed, Scarpetta trailblazers.
But in recent years programmes such as CSI, NCSI, Bones, Silent Witness and Waking The Dead have grabbed television audiences by the throat and held them captivated. Why, I wonder, was Scarpetta not at the forefront of the forensics revolution on screen as well as in print? Did nobody recognise her potential as television gold? And with that, Cornwell becomes animated and outspoken. It's an issue that clearly touches a very raw nerve.
"Scarpetta opened the floodgates that enabled other people to use forensics in a crime fiction context," she says, in frustration. "I like to give her credit but whoever you want to credit, it was a real shock when I woke up one day and saw my career on screen; suddenly the schedules were full of forensics. In an ideal world that would have been Scarpetta; it should have been Scarpetta but she was tied up and held hostage."
Her hostage-taker in this case was Hollywood; Cornwell handed her creation over of her own free will, confident that the movie options would lead to a movie. But it has still not been made.
"Unfortunately Scarpetta was tied up and meanwhile anybody could pick up my books and take what they wanted," she says. "It's been a big disappointment to me that the movie has taken this long; I have high hopes that something is finally happening, so it better be big and it better be good and it better be worth it."
No pressure, then. But Cornwell drives herself harder than anyone. She weaves in references to cybercrime, the latest ballistics research and, in this new book, successfully touches upon the growing spectre of international terrorism. It's all about much more than giving her readers the adrenalin-packed ride of their lives.
"Crime novels are a great excuse to get people together and to look at society and examine issues that affect us all," she says. "The crime is just the party to get the people to show up. Scarpetta gets stuck in the same traffic jams as we do, she suffers the same modern stresses, she has to deal with social media in a recognisably contemporary setting."
Whether serial killers or remote random snipers correspond with any party most of us have ever attended is a moot point. But Cornwell sees it as not just her job, but her vocation, to draw us into the very cinematic world she skilfully conjures up with her deceptively literary prose, which generally goes unremarked upon.
"To be a good writer you need to be self-aware, not self-indulgent," she says. "You are taking your readers on a journey, and sure, it would be nice to get recognition for some of my turns of phrase, but at the end of the day it's all about the reader. There's a sense of achievement in transporting readers to a place without them even noticing how they got there."
Flesh and Blood (HarperCollins $36.99) is out now.
