After the two-factor model, the three-factor model was developed adding more traits present in psychopaths. Those three factors are:
1. Arrogant and deceitful with others;
2. Lacked affective experiences;
3. Impulsive and irresponsible.

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Dr. Hare's checklist includes 20 items which correspond to different traits present in psychopaths. This checklist began with the two factor model and later expanded to a three and four factor model. The numbers listed on each item's row corresponds to the factor it relates to.

The 20 Items on Hare's Psychopathy Checklist 

Kiehl, K. A., & Hoffman, M. B. (2011). THE CRIMINAL PSYCHOPATH: HISTORY, NEUROSCIENCE, TREATMENT, AND ECONOMICS. Jurimetrics, 51, 355–397.

Relationship between crime and psychopathy

Three-Factor Model in Hare's Psychopathy Checklist

After the three-factor model, the four-factor model was developed adding even more traits present in psychopaths. Those four factors are:
1. Interpersonal;
2. Affective;
3. Lifestyle;
4. Antisocial.

Four-Factor Model in Hare's Psychopathy Checklist

Dr. Hare's checklist began with the two-factor model. This includes the following items:
1. Interpersonal-affective;
2. social-deviance.

Two-Factor Model in Hare's Psychopathy Checklist

Many clinicians use Hare's Psychopathy Checklist to diagnose patients with psychopathy. To do this, after talking to the patient, the professional will score each criteria based on how much it fits the person's personality. The grades range from 0 (does not fit), 1 (kind of fits), to 2 (definitely fits). After grading every criteria, the clinician adds all scores with the maximum being 40 and the minimum a zero. According to Hare, a person is a psychopath if they receive a score of 30 or more.

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