Mr. Specter. Would you describe what you mean by a control question?
Mr. Herndon. The control question is the question on which you would expect the examinee to probably lie, or have some emotional response which can be used for comparative purposes with regard to the relevant questions of the interrogation.
Mr. Specter. Would you give an example of what you mean by control question, then?
Mr. Herndon. Yes, I can.
In a bank embezzlement case, a good control question with an individual might be, “Have you ever stolen anything in your life that didn’t belong to you?”
In that regard it is expected the person would probably either hedge or deceive, and, therefore, the examiner can usually have an indication of whether or not this person will respond to a deception based on the examinee’s response to that question.
Mr. Specter. Mr. Herndon, what is the policy of the Federal Bureau of Investigation on the use of the polygraph examination?
Mr. Herndon. The FBI uses the polygraph technique purely as an investigative aid, in very carefully selected cases.
As I have said before, we feel that the polygraph technique is not sufficiently precise to permit absolute judgments of deception or truth without qualifications. The polygraph technique has a number of limitations which must be considered by the examiner. The instrument, again, I said before, is designed to record under proper stimuli emotional responses in the form of physiological variations which may accompany and indicate deception.
Mr. Specter. What effect, if any, would there be on a polygraph examination if the subject were a psychotic depressive with respect to mental condition?