I met Charles at the Behavioural Medicine Institute Atlanta, where he was visiting to complete lie detector tests on a physician going through an evaluation programme for treatment for sexual boundary violations. The question he was to be asked was "Have you ever had sexual intercourse with any of your patients?"The polygraph consists of a sensor array connected to software via a connecting device. One sensor is a pad placed on the chair of the interviewee, with coiled expanders placed around the chest, pads on the skin and an inflatable tourniquet around the arm.
They measure heart rate, respiration and perspiration, all of which are known to alter when a person is lying. Once the subject is hooked up the polygrapher typically starts with general questions, 'what day is it, what's your name' and so forth. The graphs on the screen (the Hollywood cliche of ink rods on paper has not been used for a long time) indicate when there are changes and Charles inputs the question he asked underneath them, in order to have a verifiable record. The computer is also hooked up to a camera which records the whole interview and is played alongside the graph record. The initial questions are there to provide a baseline for changes to heart rate, respiration or sweating. Questions alternate between the mundane and easy to answer to the questions, in these cases regarding sexual behaviour with patients, which have been set by the Institute doctors.
Charles says that the most reliable results are gained from single issue tests, which he says result in a 90-95% validity rate. So mulitple issue, many questions tests have a lower chance of providing an accurate indication of the truth.
Polygraphers have to have 400 hours of initial training over ten weeks, including basic phsyiology, psychology and in the use of the polygraph instrument. This is followed by obligatory mentoring for the first 200 cases and by advanced training for working in sepcialist areas, such as with post conviction sex offenders. Whilst polygraphs are fairly widely used in the US they are not admissable in open court so tend to be used for monitoring sex offenders, as well as for initial police investigations. The courts will take them into account, but only alongside a range of evidence from different sources. This too is the approach taken by Dr Abel at BMI, who sees it as an indicator only and doesn't base treatment decisions on its results alone.
About half of US states register and regulate polygrpahers and practitioners belong to a professional association which obliges them to keep their training up to date.
Charles says that the tests are not useful for people in psychotic states, people with Tourette's or for psychopaths.
And the physician being polygraphed? When asnwering the question each time his heart rate increased, his respiration changed and he perspired. For Charles this meant he was certainly lying, for Dr Abel it was just an indicator, part of a bigger prgramme of evaluation and assessment.
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