Psychopaths are a natural phenomenon that exists at a frequency that confers an evolutionary advantage. There are various definitions of a psychopath, and some attempts to separate the terms psychopath and sociopath. I use both terms interchangeably. The trouble I have with any definition is that it is heavily weighted by the context in which the diagnostic criteria have been arrived at. Dr Robert Hare is perhaps the most famous clinician associated with the diagnosis and his experience is typical - the psychopaths that sparked his interest and, more importantly, informed his diagnostic criteria, were all in prison.
I haven't read of any weighty criticism of this - basing criteria for a psychological diagnosis on a very obviously skewed sample. I guess it is understandable because society only really has motivation to diagnose and understand people who are different when they impact society - and most diagnoses are court-ordered for offenders.
I see psychopathy as being a spectrum (of thought pattern), and for the diagnosis and understanding of it to be critically based on criminal behaviour is disingenuous at best.
The definitive traits of the psychopath certainly make them more likely to be a criminal, but that is hardly the full story, just as not all young black men in ghettos are criminals. We live in a scientific age where we can analyse genes and image brains as they function - more research is needed to catch budding psychopaths when they are young so that behavioral treatments can be given as soon as possible. The evidence so far is that genes and environment play a part in the development of a psychopathic personality. Given the right environment, I have no doubt that those with psychopathic tendencies have the potential to be not just honest and productive members of society, but valued for contributions that an empath simply couldn't provide.
So what are the diagnostic criteria I consider essential? At a neurological level, there are noted differences in the brain structure of psychopaths - though care should be taken that physical criteria like this are also not simply associated with criminal tendencies, such as low impulse control. I think essential to a diagnosis would be a lack of empathy and remorse/guilt. There is also a lack of normal physiological response to usually emotive words - a psychopath would likely fail the Voight-Kampff test.
Further than that, it seems to me that there is also a lack of societal bonds - social situations are learned and used to form consciously decided impressions, and there is an instinctive feeling that the rules of society do not apply to them.
I expect to still be alive when genome sequencing and neurophysiology scans become routine for the richer half of the populations of the western world. This will advance the understanding of many psychological diagnoses to a level we can only dream of today. The only question is whether society will see it as a manageable neurodiversity, or as a disorder that needs to be eradicated (strong genetic tendency = abortion?).