Psychologist S.K. Henderson described psychopaths in his 1939 text as follows:

The term psychopathic state is the name we apply to those individuals who conform to a certain intellect standard, someones high, sometimes approaching the the realm of defect but yet not amounting to it, who throughout their lives, or form a comparatively early age, have exhibited disorders of findings of an antisocial or asocial nature, usually of a recurrent or episodic type, where, in many instances, have proved difficult to influence by methods of social, penal, and medical care and treatment and for whom we have no adequate provision of a preventive or curative nature. The inadequacy or deviation or failure to adjust to ordinary social life is not a mere wilfulness or badness which can be threatened or thrashed out of the individual so involved, but constitutes a true illness for which we have no specific explanation.

The official psychiatric term for a psychoapth is antisocial personality disorder. The diagnostic criteria for this disorder, as described by the standard Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV), are as follows:

• There is a pervasive pattern of disregard for and violation of the rights of others occuring since age 15 years, as indicated by at least three (or more) of the following:

1. Failure to conform to social norms with respect to lawful behaviors as indicated by repeatedly performing acts that are grounds for arrest.
2. Deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure.
3. Impulsivity or failure to plan ahead.
4. Irritability and aggressiveness, as indicated by repeated physical fights and assaults.
5. Reckless disregard for the safety of self or others.
6. Consistent irresponsibility, as indicated by repeated failure to sustain consistent work behaviour or honor financial obligations.
7. Lack of remorse, as indicated by indifference to or rationalizing having hurt, mistreated, or stolen from another.

• Individual is at least age 18 years.

• There is evidence of Contuct Disorder with onset before age 15 years.

• The occurrence of antiosocial behaviour is not exclusively during the course of a Schizophrenic or Manic Episode.

• Evidence of conduct disorder onset before age fifteen.

Psychopathic Checklist

Without Conscience: The Disturbing World of the Psychopaths Among Us - has devised a twenty-item checklist identifying the main characteristics of the psychopathic personality.

1. Glib and superficial charm - the tendency to be smooth, engaging, charming, slick, and verbally vacile. A psychopath never gets tongue-tied.
2. Grandoise self-worth - a grossly inglated view of one’s abilities and self-worth. Psychopaths are arrogant people who believe they are superior human beings.
3. Need for stimulation or proneness to boredeom - an excessive need for novel, thrilling, and exciting stimulations; taking chances and doing things that are risky.
4. Pathological lying - can be moderate or high.
5. Conning and manipulativeness - the use of deceit and deception to con, cheat, or defraud others for personal gain.
6. Lack of remorse or guilt - a lack of feelings or concern for the losses, pain, and suffering of victims.
7. Shallow effect - emotional poverty or a limited range or depth of feelings.
8. Callousness and lack of empathy - a lack of feeling toward people in general; cold, contemptuous, inconsiderate, and tactless.
9. Parasitic lifestyle - an intentional, manipulative, selfish, and exploitative financial dependance on others.
10. Poor behavioral controls - expressions of irritability, annoyance, impatience, threats, agression, and verbal abuse.
11. Promiscuous sexual behavior - a variety of brief, superficial relations, numerous affairs, and an indiscriminate selection of sexual partners.
12. Early behavioral problems - a variety of behaviors prior to age thirteen, including lying, theft, cheating, vandalism, bullying, sexual activity, fire-setting, glue-sniffing, alcohol use, and running away from home.
13. Lack of realistic long-term-goals - an inability or persistent failure to develop and execute long-term plans and goals.
14. Impulsivity - the occurrence of behaviors than are unpremeditated and lack reflection or planning; inability to resist temptation.
15. Irresponsibility - repeated failure to fulfill or honor obligations and commitments.
16. Failure to accept responsibility for own actions - as reflected in low conscientiouness, an absense of dutifulness, denial of responsibility, and an effort to manipulate others through this denial.
17. Many short-term marital relationships - a lack of commitment to a long-term relationship.
18. Juvenile relinquency - behavior problems between the ages of thirteen and eighteen.
19. Revocation of conditional release - a revocation of probation or other conditional releases due to technical violations.
20. Criminal versatility - a diversity of types of criminal offences; taking great pride in getting away with crimes.

Psychopathic Checklist

Without Conscience: The Disturbing World of the Psychopaths Among Us - has devised a twenty-item checklist identifying the main characteristics of the psychopathic personality.

1. Glib and superficial charm - the tendency to be smooth, engaging, charming, slick, and verbally vacile. A psychopath never gets tongue-tied.
2. Grandoise self-worth - a grossly inglated view of one’s abilities and self-worth. Psychopaths are arrogant people who believe they are superior human beings.
3. Need for stimulation or proneness to boredeom - an excessive need for novel, thrilling, and exciting stimulations; taking chances and doing things that are risky.
4. Pathological lying - can be moderate or high.
5. Conning and manipulativeness - the use of deceit and deception to con, cheat, or defraud others for personal gain.
6. Lack of remorse or guilt - a lack of feelings or concern for the losses, pain, and suffering of victims.
7. Shallow effect - emotional poverty or a limited range or depth of feelings.
8. Callousness and lack of empathy - a lack of feeling toward people in general; cold, contemptuous, inconsiderate, and tactless.
9. Parasitic lifestyle - an intentional, manipulative, selfish, and exploitative financial dependance on others.
10. Poor behavioral controls - expressions of irritability, annoyance, impatience, threats, agression, and verbal abuse.
11. Promiscuous sexual behavior - a variety of brief, superficial relations, numerous affairs, and an indiscriminate selection of sexual partners.
12. Early behavioral problems - a variety of behaviors prior to age thirteen, including lying, theft, cheating, vandalism, bullying, sexual activity, fire-setting, glue-sniffing, alcohol use, and running away from home.
13. Lack of realistic long-term-goals - an inability or persistent failure to develop and execute long-term plans and goals.
14. Impulsivity - the occurrence of behaviors than are unpremeditated and lack reflection or planning; inability to resist temptation.
15. Irresponsibility - repeated failure to fulfill or honor obligations and commitments.
16. Failure to accept responsibility for own actions - as reflected in low conscientiouness, an absense of dutifulness, denial of responsibility, and an effort to manipulate others through this denial.
17. Many short-term marital relationships - a lack of commitment to a long-term relationship.
18. Juvenile relinquency - behavior problems between the ages of thirteen and eighteen.
19. Revocation of conditional release - a revocation of probation or other conditional releases due to technical violations.
20. Criminal versatility - a diversity of types of criminal offences; taking great pride in getting away with crimes.