Polygraph Expert Witness – Polygraph Examiner – Polygraph Instruments



Polygraph 101 – An Outline An article by Kenneth E. Blackstone A polygraph examination is composed of three phases, and every minute should be videotaped by the examiner. The first phase, the pre-test interview, includes a review of physical and mental health history, establishing the purpose of the examination, an explanation of the polygraph instrument, signing of a release form, review of personal history, and then a review of questions that will be asked during a second phase of the examination known as the in-test. While questions differ per issue, the questions asked must meet a specific standard. The examinee is not attached to the polygraph instrument during the pretest interview. The second phase, the in-test or physiological measures, involves using an instrument to monitor the autonomic nervous system of a person while that person is answering pre-reviewed questions. The attachments are non-invasive and the basic attachments are two pneumographs that record respiration -- one GSR (galvanic skin response) instrument, which measures electro-dermal activity that is the result of perspiration, and one cardiograph, which records blood volume and pulse. There are two types of polygraph instruments, analog and digital; both recording devices have the same attachments. Analog instruments look like suitcases, and tracings are made by ink pens on graph paper pulled by a kymograph, while the digital instrument uses a DAS (digital acquisition system) to convert these movements into digital value and send them to a computer. The third phase, or post-test interview, is for a review of the examination with the examinee. This phase is optional, in that the examiner may have been directed by the referring party to pursue or not pursue deceptive responses. See the article Polygraph 102. Kenneth E. Blackstone is a certified polygraph examiner and expert witness regarding the proper use of polygraph in civil, clinical and criminal testing settings concerning polygraph procedures used in the evaluation of accusations of rape, kidnapping, homicide, child abuse, molestation, sexual harassment, and shaken baby syndrome, and during sex offender management and civil commitment proceedings. He has been involved in more than 23,000 polygraph examinations and has conducted more than 15,000 polygraph examinations. Home \| Clients \| Credentials \| Articles \| Contact Copyright © 2007-08 Kenneth E. Blackstone, All Rights Reserved. Site composition by Expert Communications Website Design by Jenny Duarte	Attorney Comment: “I was a guardian ad litem; I read his report and heard his testimony and have used Ken since then on everything.” Prosecutor Comment: “Your testimony was some of the best I've heard as a prosecutor, and your objectivity restores my faith in polygraph.”