Down by the sea, there's a freshly dug pit in the sand.

It's probably the work of a dog or some kids with spades, but I'm just about to meet crime writer Val McDermid so it strikes me that it looks a little sinister too, like a grave waiting for a body. And isn't a beach the kind of place where bodies turn up, or are disposed of, where evidence can be destroyed, or hidden in the sand or thrown in the water where the police won't find it? All crime writers should live by the sea.

I don't realise how close this is to the truth until I meet McDermid at a coffee shop close to the beach. She arrives, cheeks reddened by the gales, and orders a latte. Large or small, asks the waiter. "Large," she says, laughing. "Do I look like a woman who's ever had a small anything?"

The former journalist, who's just finished her 26th novel, has lived in this village by the sea in Northumberland for nine years now with her wife, who's a publisher, her son and a raggedy border terrier. They live in a cottage by a courtyard where McDermid also has an office. Just by the door there are two baby swallows in a nest, keeping constant watch like a couple of detectives on a stake-out. It's a pretty place, but McDermid writes about blood and killing, so every day she walks down to the beach and trudges along the sand where she can think about murder.

"Walking by water frees your creativity," she says. "I don't know how it works – there's something about it that's liberating." She suspects a lot of crime writers live by the sea – Agatha Christie certainly did – and tells me that just a few months ago a body was washed up here. "Everybody thought it had something to do with me," she says.

She starts to talk about that 26th novel – The Vanishing Point – which is one of the standalone books she writes when she's not doing her series about criminal profiler Tony Hill. Those books are about a man trying to untie all the ugly knots of a serial killer's brain, but The Vanishing Point focuses on reality TV and a character named Scarlett Higgins, whose son is kidnapped at an airport, and was inspired by something that happened to McDermid.

"I was travelling with my son when he was about six," she says. "I've got replacement knees so I set off the detectors, and they literally put you in a box. While I was there, my boy was standing by the luggage belt waiting for our bags to come through and I thought that someone could just take him by the hand and walk away with him."

It's taken a few years – and a few walks along the beach – for the idea to become a novel, and the result delves into some interesting parts of McDermid's philosophy. She isn't the kind of writer who makes points in her books – the point is the narrative – but there were clearly a few things on her mind when she was writing The Vanishing Point, such as how a society protects itself from crime.

She thinks we have become too fearful of crime and that this has led us to dangerous places. "Sometimes fear is used as a way to control," she explains. "Many of the systems put in place are not about terrorism or crime. They're about control. The number plate recognition that covers huge swathes of the country for instance – what's that for? Why do the police need to know where I am? In the hands of a benevolent government, they could be looking after your interests, but what if the next government isn't so benevolent?"

The other issue at the heart of The Vanishing Point is reality TV. McDermid has a vague distaste for the genre, but respect for some of those who participate. "A lot of reality TV is repellent but that doesn't diminish the qualities of some of the people who take part. There are decent people in there who have no alternatives."

She believes reality shows have now joined sport and pop music as one of the escape routes from poverty or lack of opportunity.

"When I was growing up, very much working class, the attention was focused on people escaping in a positive way – the message I always got was that the way out was education."

Which is exactly what happened. At school in Kirkcaldy, McDermid was chosen for fast-track education, went on to Oxford, worked as a journalist and has now been a novelist for 25 years. However, there is a through-line in it all: a self-deprecating philosophy inherited from her father and Robert Burns that amounts to "put something back", "a man's a man for a' that" and perhaps "don't get above yersel".

McDermid has a similar egalitarian approach to her work: literary snobbery gets on her nerves, as does the labelling of books as crime or Scottish crime, which for her always has a whiff of judgment about it: "We have a huge readership who aren't people who are somehow intellectually diminished. It's not just stupid people who read our books. And labels are for booksellers and publishers. You might as well put writers who are 5ft 5in tall together."

If it was up to her, McDermid would organise all fiction together, arranged from A to Z, and she certainly doesn't believe in a gay section. "Some lesbians write lesbian fiction that's targeted at a lesbian audience, and that's fine," she says. "I don't write that kind of book. I've never wanted to live in a ghetto and I don't want to write in a ghetto. You don't do your washing in a particularly lesbian way. You don't go to Sainsbury's in a particularly gay way. It's part of a landscape and it's important to me to be part of that landscape."

McDermid says she sees herself on a literary landscape made up of Jekyll And Hyde and Confessions Of A Justified Sinner rather than Agatha Christie or Dorothy L Sayers ("Lord Peter Wimsey? There's a man with a face you'd never tire of slapping"). She also believes her genre will always be popular because crime novels represent a sublimation of our natural violent instincts. At some level, she says, we all want to be violent and must work to suppress it.

"It's particularly true for women," she argues, "because we're raised not to be confrontational and that masks the fact we have these feelings of violence. We feel angry, we feel like hitting somebody, but we have nowhere to put that, which is maybe why a lot of women are learning how to box. I'd much rather they read crime fiction. I've killed lots of people I don't like."

And she usually kills them in a horrible way too: in a Val McDermid book, you're only ever a few pages away from a nasty act of violence, and the author prefers that to the elegant, bloodless deaths of Christie or Sayers. She says her way is more honest about the fact that many of us get excited by reading about violence.

However, she does have a line: she will not linger lovingly over a dead body and, in fact, is rather squeamish. It took years, for instance, for her friend, Sue Black, professor of anatomy at Dundee University, to convince McDermid to enter an anatomy lab. And when she did, the crime writer held a human heart in her hand and saw human intestines mounted on a board, looking, she says, like jewellery. It was an intimate, moving experience for her and strengthened her belief that if something discomforts you, it's often better to walk towards it.

McDermid says this is what she's doing in her novels, and it's a good thing. She doesn't know if books like hers encourage or desensitise us to violence, but she does believe her books are moral: not only do bad things happen to bad people, they also put us in extreme places and make us ask extreme questions. She also wants readers to enjoy the books, of course, because she certainly does. She may be writing a non-crime novel next – of all things, a modern reimagining of Northanger Abbey set at the Edinburgh Festival – but then it's straight back to the Tony Hill books because crime is what she loves.

"When you're writing a novel," she says, "there's nothing more exciting than having a dead body on the premises."

The Vanishing Point by Val McDermid is published by Little, Brown at £16.99.