JK Rowling took children's fiction to the realms of nightmare in her Harry Potter series. From spectral dementors who sucked out the soul through a deadly kiss, to a demonic snake that swallowed its victims live, everything was left to the child's imagination - once it had been shaken and stirred by her pen. It wasn't just physical violence that confronted the boy wizard and his friends: he had to contend with parental loss, betrayal, loneliness, bullying and, finally, the embodiment of evil itself.

We now hear that Rowling has been seen scribbling in an Edinburgh cafe. She is rumoured to be turning her talents to crime fiction. In a week in which Ian Rankin and Val McDermid have been in friendly dispute over the levels of violence in the work of women crime writers, it looks as if the stakes are about to be raised. It wouldn't surprise me if Rowling's crime fiction was the darkest yet.

Rankin said in an interview last year that people writing the most violent novels today are women. He allegedly added: "They are mostly lesbians as well, which I find interesting." He later said that to get into the top 10 "it helps if you're a woman if you write violent books. It helps if you're a man if you don't".

Val McDermid took issue with his remarks. I don't see why. There is violence in her work as there is in Rankin's, whether more or less is harder to determine. But if women write more violence than men, so long as it is well written, does it matter? We only have to remember Agatha Christie and Dorothy L Sayers to be certain that writing about violence is a far cry from perpetrating it. Does the sexual orientation of the woman matter? It doesn't to me.

If more women than men are among the top 10 crime writers, presumably it's because readers clearly think women write it better. I can entirely see why it should be so. Men are more likely to be practitioners of violence. It's men who get into punch-ups, brandish knives and carry shooters. It's men who go to war. The Kray brothers didn't ever threaten to "send round the girls". Masculine writers are, therefore, more likely to have an insight into male rage.

A woman's accepted place in a violent world is victim. That's a very important role in violent fiction. Understanding how the victim feels brings a different reality to the text. Also, while women are very rarely overtly violent, they can be vicious, unkind and spiteful - all forms of aggression. On the rare occasions that a woman becomes a killer, her actions will be the result of a slow burn, yet nonetheless deadly. Women make excellent plotters in real life, so why wouldn't they write about it?

Women also have a very corporeal view of the world. The delicacy of women is a long-perpetuated myth that is encouraged to exist alongside, and in contravention of, the evidence. It is largely men who drive home the knife or pull the trigger but it's women who pick up and care for the wounded. They see and handle the slashed and the shot, the dismembered or disembowelled. What happened to the Glasgow Airport bomber with self-inflicted 90% burns between the time we saw him being dragged along a wet pavement and his death? He, like all the wounded, was taken to hospital where nurses, still mostly female, dealt with his wounds. Theirs is a task that would make many men faint.

Women bear babies and change nappies. They nurse the sick and care for the elderly. When victims die violent deaths, their sad, battered bodies will be washed and laid out by, mostly female, nurses or wives or mothers. It gives women a true and unvarnished understanding of the pathos and destructiveness of violence. It also toughens them. So don't let us continue to kid ourselves that it is beyond a woman's ken. When it comes to graphic descriptions of what it is to be physically or sexually violated, women are better placed than men to write them.

In the wake of the murder of the Polish student Angelika Kluk, there was an interview with the pathologist who worked on her case. Attached to it was a full-page picture which was, in effect, the crux of the story. The pathologist was a young, pretty, fine-boned blonde woman. The implication was obvious: isn't it shocking that so delicate a creature should be exposed to such horror? The newspaper described the hot, cramped conditions under the church floor where she worked for hours, gathering evidence from Kluk's body. It failed to spot the irony that her ordeal wasn't a patch on what the delicate, blonde, young Kluk had undergone.

It is an attitude that is implicit in the television series Silent Witness, in which Amanda Burton plays a thoughtful pathologist. It also underpins the work of graphic writer Patricia Cornwell, whose lead character, Kay Scarpetta, is a pathologist. Frequently she works alone at the morgue in the middle of the night. It's often just her, a corpse and the whirr of her bone saw in the empty building, even when there is a serial killer on the loose and after her. The reader is left biting their nails.

Is it shocking that women work in or write candidly about the underbelly of life? Not at all.

Women writers, whatever their sexual orientation, may just be better equipped to tell murder and torture like it is. If so, why would they hold back? Their readers watch the news and read the papers. They have seen real-life cases in Scotland where a head washed up in one location and a leg in another; heard of a young woman running along the motorway with half her forearm missing and of a family man gunned down on his own doorstep while his wife was bathing their children. They go to bed night after night with carnage in Iraq as a side dish to their bedtime drink.

Readers are not then going to pick up a thriller expecting to have the cadaver covered with a literary doily. Reading about a victim swathed in euphemism would be like eating an egg without salt.

Ill-written scenes of violence wash over the mind, while well-drawn images stay. One of P D James's earlier works opens with a corpse in a rowing boat, its hands severed at the wrist. It is an image that remains, like that of two young men tipping silently backwards off the Forth Road Bridge. The latter was Rankin. It wasn't bloody, yet I see the pair in my mind's eye every time I cross to Fife.

The two most terrifying writers for me, the two who caused me to sleep with the light on, are male. One is Thomas Harris in his novels Red Dragon and The Silence of the Lambs; the other is Henry James in The Turn of the Screw. Harris is graphic; James is not. What is frightening is the exposure of the characters (and, therefore, the reader) to something "other"; to something uncontrollable.

Something evil and "other" was the challenge that Harry Potter had to face down. What blood-curdling tales might Rowling now be concocting for adult readers? I, for one, can't wait.