In Assessing the Truth: How Forensic Psychiatrists and Psychologists Evaluate Litigants, Dr. Mark Levy, a Distinguished Life Fellow of the American Psychiatric Association and forensic psychiatry expert witness writes:
With regard to causation, the forensic expert must always be on guard to not fall into the trap described so artfully more than 200 years ago by a great physician and man of letters, Samuel Johnson: “It is … physicians, I am afraid, beyond all other men, [who] mistake subsequence for consequence.” In other words, just because B follows A does not mean that A caused B.
In addition to reviewing medical (and sometimes military, employment and academic) records as well as legal documents such as the complaint and deposition transcripts, the forensic psychiatric evaluator examines the plaintiff himself, usually for several hours, inquiring about his personal, developmental, social, family, marital, medical, drug, educational, employment, academic and legal histories. This interview takes a long time because it takes a long time to hear someone’s life story; there are no shortcuts to extracting this kind of essential narrative.