From the earliest days in my career as a criminal forensic psychologist, I have encountered treatises and learned discussions about the difference between psychopaths and sociopaths. Still, to this day, I have never had reason to use the terms, other as than synonyms.
From my days in training, I recall a psychiatrist saying that a Mafia don (referring to The Godfather) was different from other criminals. The Don could be called a sociopath - his "pathology" consists of having moral values that diverge from those of society. The psychiatrist reserved the term "psychopath" for a different class of criminal - blood lust killers, for example.
The standard diagnostic term for those with a criminal orientation is antisocial personality disorder.
In the DSM-II (page 43) - the diagnostic manual in use when I trained - antisocial personalities were described as "unsocialized" individuals who were selfish, impulsive, irresponsible, and in conflict with society. Incapable of feeling guilt, they characteristically blame others and excuse their own transgressions. Criminal behavior alone was not enough for the diagnosis, nor was "social maladjustment."
More specific criteria were established in the next edition, DSM-III. The fourth edition (DSM-IV, 1994) noted that the antisocial pattern "has also been referred to as psychopathy, sociopathy, or dyssocial personality." That language was preserved in DSM 5.0.
In practice, antisocial personality is a relatively useless diagnosis. It describes many common criminals, but it does not convey a sense of the evil and depravity displayed by some. Additionally, the diagnosis does not apply until someone is either caught or their enterprise fails, when it becomes a problem or source of distress.
To be useful, a label or diagnosis must serve to summarize and communicate something specific. The antisocial diagnosis is typically used simply to indicate that the person has a criminal history. The term tells us little about their attitudes, values and beliefs, and almost nothing about their motivations or psychological dynamics.
The most commonly used "test" for antisocial personality disorder is the Psychopathy Checklist (PCL-Revised). It is not actually a test that can be taken, but instead, an assessment protocol involving clinical ratings and a review of the individual's history. How useful it is for what purposes is always a matter of debate. What the PCL-R does provide, however, is a description of the emotional and interpersonal style of a psychopath, and the personality traits that contribute to deviant behavior.
Theorists seeking to distinguish psychopathy from sociopathy often focus on whether there was violence involved in the signature behavior, or whether it was just a matter of thievery and deceit. With this formulation, O.J. Simpson might be called a psychopath, and Bernie Madoff would earn the title of sociopath.
Neither the DSM or the Psychopathy Checklist makes the above distinction. The diagnostic formula applies similarly to the psychopath lurking outside your window and the sociopath in the executive office.
To account for the difference between killers and con men, some theorists say that violent and aggressive sociopathy results from genetics. In contrast, they say that the cunning and manipulative learned to be that way.
In the science and the literature, when it comes to psychopaths, there is no essential distinction to be found between the influence of heredity versus the environment, or between nature and nurture. The consensus understanding is that biology and experience are both involved in shaping psychosocial development. The Bad Seed theory of criminality has never been a sufficient or sufficiently general explanation.
In the context of forensic psychology - applying theory and data to legal questions - there is no use at all in labeling some as psychopaths and others sociopaths. What matters is understanding the psychological corruption and deviant behavior of the individual character.
Irrespective of the individual characteristics, there remains a unifying factor underlying the psychopathic mind: the dynamics of pathological narcissism and the grandiose self.
The profile is that of someone who fervently believes in their own goodness, wonder and rectitude, therefore feeling righteous and entitled, justified and innocent, no matter what their sins. They believe that people get what they deserve, tending to view themselves as uniquely deserving and others as generally unworthy. Your rights are of no concern to them if you have what they want or get in their way.
It makes no difference what you call them - psychopath or sociopath - or how critically you assess them. They are armed with self-righteousness and are immune to invective. As an alternative, you may also refer to psychopaths as chameleons, vultures or scorpions.