Is there a psychopath in your inbox? Measuring psychopathy only began as a science in the Forties and the current international gold standard for the diagnosis of psychopaths - the Psychopathy Checklist Revised (PCL­R) - was devised by Dr Robert Hare in 1991. In this checklist, the 20 fundamental qualities of a psychopath are outlined, giving a maximum score of 40. Most of us sit somewhere on this scale of psychopathy: fine, upstanding citizen that I am, my own PCL­R score is four. A serial killer would score somewhere between 30 and 40. "Borderline" psychos score somewhere around 20 to 25. These are the ones who may not even commit a criminal act (bar some petty thieving in their childhood) but are "successful psychos," passing themselves off as normal in the real world. Often they hide in the corporate world where their motivating forces of greed, risk­-taking behaviour and egotistical avarice are seen as, at best, commonplace behaviour, at worst, necessary for success. It is these "wolf in sheep's clothing" types that we are most likely to have a brush with. These "sub­criminal" psychopaths may be particularly intelligent or well educated, less haphazard than the typical (criminal) psychopath, have developed highly polished social skills and managed to insert themselves into an echelon of society where they are accepted and trusted - as a lawyer, stockbroker or even psychiatrist. Their behaviour may not be illegal - not quite - but it is immoral and potentially devastating, as they manipulate, bully and frighten their close family, friends, colleagues and associates into keeping quiet about their misdemeanours. The PCL­R checklist items cover lifestyle factors such as juvenile delinquency, promiscuity, lack of realistic long-­term goals and personality traits including superficial charm, pathological lying, lack of empathy and impulsivity. To be a certified psychopath, you need to score in both areas. But not all psychopaths are created equal and just because one or two features are missing from the assessment, doesn't mean they don't fit the overall picture. Plus, just because you meet someone who, for example, leads a parasitic lifestyle but is otherwise unexceptional, it doesn't make them a psycho. They may just be a sponger. If you develop close feelings for a psychopath it is likely to be disastrous; their emotional life is a dry and arid place. It's not that they have no emotions at all, but they are short-lived and shallow. I can assure you that a psycho will never fall in love with you. "I buy her flowers and tell her I love her with all my heart," one client told me, of his girlfriend. I don't really know what that means, but I know that it puts a smile on her face and buys me what I want from her. Flowers are cheaper than paying my own rent. This lack of feeling means a psycho will apparently switch emotions in a millisecond for no apparent reason, one moment crying about their childhood traumas (they often believe they were maltreated outsiders), the next complimenting you on your nice teeth. The pointers (left) should help you to identify if you're dealing with a psycho but I'd also advise using your gut instinct. If a date makes you feel uncomfortable - in other words, in the very scenario in which they should be trying to put you at ease - then take note. Even I still use the unscientific "hairs on the back of my neck" scale to alert me to danger in an interview scenario. Your best protection against a potential psychopath is a strong sense of your own boundaries: if you feel that someone is making you cross over a line then consider carefully if they should be in your life at all. The good news is that as soon as a psychopath senses that you are not going to allow them to be a freeloader on your life - whether it's money, sex or doing their work for them - they'll move on as quickly as possible. It is fruitless to confront them - being accused of being a psycho will either make them angry or, perversely, they'll take a pride in it. But you don't have to have them in your life - and knowing who they are means you can take steps to end your association with them or at least limit it greatly. Flagging it up If there's someone in your life you think could have potential psychopathic elements, ask yourself the following questions. When they talk about their childhood, do they always paint themselves as either tragic victims or valiant heroes? When talking, do they make a lot of hand gestures to emphasise their points, particularly when speaking of emotional matters? Do they "fall in love" with alarming regularity and speed, always moving in with their latest conquest... only to move out again a few months later when their partner is no longer happy to shoulder all of the rent and bills? Do they make the same mistakes over and over again, never learning their lesson? Are they slow to recognise fear or disgust in the faces of others? When you first got to know them, did you find that you were revealing a lot more about yourself than you intended to? How do they make you feel? Around them do you feel used, dominated and anxious? If caught out in a lie, do they brush it off without explanation or embarrassment? Are they enthusiastic about risky ventures - driving too fast, using drugs, unprotected sex, extreme sports or, most likely, all of the above? Do they brag about petty criminal exploits in their childhood? The good news is that if you think you're a psychopath, then by definition you almost certainly aren't (and if you are, you will have lied your way through this anyway). One or two "yeses" to the above questions doesn't make for a particularly nice person, but you'd need to tick off all of them (and more) to be a psychopath. Is There a Psycho in Your Life? by Kerry Daynes and Jessica Fellowes (Hodder, rrp £6.99), is available from Telegraph Books at £6.99 + 99p p&p. Call 0844 871 1515 or visit books.telegraph.co.uk