29/04/2012 17:24 BST | Updated 29/06/2012 06:12 BST

How Crime Fiction Gets it Wrong

The Conan Doyle formula for a popular detective story has remained virtually unchanged for over a century. The central protagonist, be he or she inside or outside the police, must be rather odd in any of a number of ways; preferably having difficulty in relating to others, or some sort of addiction that causes them to fight with their inner demons, but be gifted with a profound insight that their superiors dismiss, but which nonetheless gives the author/scriptwriter plenty of scope for moving the plot on whenever it gets stuck.

The hero's gifts may be knowledge of esoteric science and human habits, as with Sherlock Holmes, an ability to unravel puzzles as with Agatha Christie's creations, and many other fictional detectives. More recently the special insights are apparently derived some sort of cod psychology, given authority by the claim that the character is a 'Forensic Psychologist', or 'profiler'. This adds an extra psychological dimension to the drama, but the problem is that to give some action to the storyline reality has to be exaggerated and distorted in a number of ways.

For a start, most of the exciting things that are done by the hero are unprofessional, or downright illegal. If a psychologist ever hid under a bed to get evidence, as Robson Green's character does in Wire in the Blood he would be banned from any further contact with the police and probably driven out of the profession, not least because the defence would use it in court to claim that information was illegally obtained and the case would be thrown out of court. Many other fictional cases in which the psychologist 'expert' becomes an active part of the investigation and confronts the culprit would similarly jeopardise the case in court. I know this because when I have helped the police in an investigation I have not been allowed anywhere near any suspects.

Most fictional psychologists who help investigations, are little more than modern day Sherlock Holmes, offering opinions from the depths of their own insights. We are rarely given any indication of the science behind their brilliant guesses. And they never get it wrong! One series that pretends to be all mathematics is Numb3rs. This even mentioned once the software I developed for locating criminals, which I called Dragnet. But the mathematics just solves the case in a waving of scribbled formulae and spurious comparisons with studies of animals. The way some limited software provides guidance to the complexities of a major enquiry is hidden for the sake of getting the story over in the time allotted to the programme.

Furthermore, to the disappointment of the many youngsters who email me asking how they can have a career as a 'profiler', there is no such career opportunity. Forensic psychologists do many other, to my mind much more interesting, things than helping the police when they get into a mess with their investigations.

It was with the intention of getting a much more accurate picture of what forensic psychology actually is and what professionals in this area actually do, that I accepted the invitation to write Forensic Psychology for Dummies. The thorough editing process that all For Dummies books go through helped to draw out important topics that, with my quarter of a century of experience, I tended to take for granted. For example I was delighted to discover that topics I had thought were obvious, were assigned a 'strange but true' icon. I learned that many apparently complex psychological issues can be rendered readily accessible once they are turned into a bullet point list. The format also allowed me to range over what forensic psychologists do in prisons, the courts and hospitals with mentally disturbed patients convicted of crimes, and put the mythical 'offender profiling' into a realistic context. I was even able to draw attention to some of my bêtes noires with a 'myth buster' icon. Unexpectedly, the Development Editor and I found a few jokes.When the page proofs turned up I read through them with surprise at how well written the book was! One of the cartoons that are de rigueur for this series even made me laugh out loud.

Now, at least, if people want to know what forensic psychology is really about they no longer need to rely on crime fiction, no matter how enthralling the fiction is to watch.