A common feature is a lack of empathy with victims. Most serial killers (with few exceptions) understand they are committing a crime because they take care not to be caught. Antisocial Personality Disorder and Borderline Personality Disorder commonly are present. Sadomasochism is also a common feature. Depending on the shared characteristics of the victims, the serial killer may have problems with impotence, paranoia, or sexual perversions which cannot otherwise be satisfied. Paranoid Schizophrenia is a common psychiatric disorder but not universal. A diagnosis of paranoid schizophrenia, in and of itself, does not necessarily justify a finding of insanity, because “insanity” is a legal construct, not a psychiatric diagnosis.