While the term 'psycho' is often bandied around in the media without much thought to the implications of the condition, psychopathy is a very real and very dangerous mental disorder. Psychopaths are, today, believed to be products of an ill-fated perfect storm combining aspects of both nature and nurture. Recent developments in the field of neuroscience and advanced behavioural studies have established that there's likely a genetic component to psychopathy. Those predisposed to psychopathic behaviour typically possess the 'warrior gene', a genetic variant which predisposes one to violent and impulsive reactions. Of course, circumstances have a lot to do with the development of psychopathic behaviours. Traumatic experiences in childhood, in particular, are believed to trigger destructive and harmful behaviour in those already genetically predisposed to aggression and low levels of empathy. An unfortunate collision of circumstances, then, can create a serial killer. But what are the odds of one ruthless killer meeting another, someone with whom they're comfortable sharing their darkest desires and someone with whom they feel secure acting against the very moral fabric that holds society together? Is there a single dominant force leading the killing spree, and a vulnerable party following suit in the name of - warped - love? Or are killing couples more likely to be equally depraved? Either way, aren't they both equally culpable? Decide for yourself, as you read the harrowing tales of these ten real life killer couples.