USE AND ABUSE in LIE- DETECTORS

Dr. V.K. Maheshwari, Former Principal

K.L.D.A.V(P.G) College, Roorkee, India

It is said that Lie-detector tests when conducted by competent and experienced operators, are of considerable practical utility. I n the first place, with the aid of lie-detector, it is possible to detect deception with much greater accuracy than is otherwise attainable. Secondly, the instrument, the tests, and the accompanying procedure have a decided psychological effect in inducing admissions and confessions from guilty individuals.

Popularly the lie-detector is often thought of as an instrument which rings a bell or flashes a light whenever a lie is told by the person who is undergoing investigation. Unfortunately  nothing as certain and dramatic as this is available Lie detection depends on deduction, on circumstantial evidence, and on the fitting together of a large number of disparate facts. It obtains its most dependable information from a continuous and simultaneous recording of changes in blood pressure, pulse, and respiration occurring during the interrogation of the suspect. These recordings are made on an instrument or polygraph, which provides a progressive record of these various physiological responses. The polygraph itself essentially consists of a long roll of paper which is pulled across a surface at a uniform speed and on which a number of recording pens leave a permanent record of their movements. The movement of the recording pens in turn is governed by various instruments attached to the person of the subject who is being investigated. The instruments are connected to the recording pens either electronically or mechanically.

Typical of the kind of instrument used is so called pneumograph, which is used for recording breathing. The pneumograph tube, which is tied round the subject’s chest, consist of a closely wound spring covered with a thin rubber tubing; one end of the tube is sealed, while the other end is connected to the polygraphitself by means of a small rubber tube. During the test the circumference of the subjects chest increases as he breathes in and decreases as he breaths out. With each inspiration, therefore, the pneumograph tube stretches, and with each exhalation it contacts The movement of the tube produces pressure changes inside it , and these are transmitted to the polygraph and recorded there.

The theoretical rationale behind the lie detection is based on a phenomenon of psychosomatic disorders. What is meant by this somewhat ill-conceived phrase is simply that certain disorders of the body, or soma, may be caused by psychological events, such as strong emotions, and that the cure for the somatic disorder may thus be achieved by first accomplishing a psychological purge. This insistence on the close relationship between body and mind, and the interplay between the two is regarded as a modern trend , and Freud and psycho-analysis  generally are often credited with the discovery of what many people have considered a vital new truth in medicine.

Let us consider what precisely the physiological reactions are which denotes the presence of an emotion. Actually expression of emotions provide base to the lie detection. Largely these emotions can be identified because they are transmitted by a special part of the nervous system .Speaking quite broadly; we may say that human beings seem to have two nervous systems. One the central nervous system is responsible for the transmission of impulses to the skeletal musculature, which is responsible for carrying out voluntary movements.

There is, however, another system, relatively independent of the central nervous system. This has been called the autonomic or vegetative nervous system and dealt essentially with certain vital but unconscious  activities. Thus we breath our heart beats, digestion take place, hormones are pouring into our blood-stream, the amount of blood passing through different parts of the body is finely regulated in response to temperature. Our eye pupil dilateates and contracts in response to differences in brightness- all without any kind of conscious adjustment. It is these autonomic, or vegetative, responses which are so closely related to emotions. Some of the major autonomic changes accompanying emotion are familiar to everyone and do not require instrumentation for their detection, These changes include flushing of the face , excessive sweating , increase in heart rate, the drying out of the mouth, many vague visceral sensations ,and so forth. Under laboratory conditions many other more subtle  physiological changes can be observed, such as a rise in blood pressure , increased oxygen consumption , increase in the number of R.B.C and platelets in the circulating blood, liberation of glucose in the blood stream and many hundreds of others which could be mentioned.

Most of these changes appear to have an adaptive purpose; the major conditions, like fear and anger are usually the precursors of violent activity, which might be fight or flight. For both a powerful supply of blood is needed. Consequently, the heart beats faster; blood is withdran from the stomach, thus stopping digestion. It is amazing to observe the wonderful adaptability shown by our bodies in responding to urgent situations of this kind, an adaptability which owes nothing  to conscious thought and everything to an inherited response pattern developed in millions of years of evolution.

This is a rough picture of the kind of procedure employed in lie –detector test and the criteria used for establishing the presence or absence of emotions accompanying a reply. How valid is the lie-detector test, and how much reliance can be placed on it ? These are difficult questions, and before answering them we must consider certain factors which affect the interpretation of scores.  One of the main difficulties in tests of this kind is the nervousness shown by many a truthful and innocent person under the conditions of police interrogation. Such nervousness is usually manifested in the record by the general erratic character of the tracings, and by large the failure of the larger reactions to be related specifically to the pertinent questions; thus , the psychological disturbances associated with nervousness appear on the lie detector record without any consistent relationship to any particular question or questions.

The lie-detector test efficacy at the present time is reasonably well known and its value in producing true confessions is without doubt. It does not in anyway partake of ‘third degree’ methods;it does not cause physical pain to the accused; and it does not, when it fails, fail by implecating the innocent person Its failure rather is a failure to detect the person who has lied.Lastly in many cases it serves as a shield to the innocent person. Who without fault of his ownis enmeshed in a mass of circumstantial evidence, but the truth of whose protestations of innocence is verified by the lie- detector .Similarly the cases where the evidence on either side is  unconvincing  and incapable of circumstantial corroboration,(Sexual crimes often fall into this categort, as in most cases none but the two persons involved are present, and physical evidence as to precisely what happened is rarely forthcoming) . In those circumstances, where any decision reached on the basis of available evidence  would be little more than guess-work there is little doubt  that the utilization oflie-detector test results  would substantially  increase the accuracy of the final decision.

Certain rules must be followed in interpreting these reactions, however ,the main rule being that in order to be considered as evidence of lying, a physiological response to a relevant question must be quite different to the physiological response to an irrelevant question. Many people, although innocent of the crime under investigation, have a bad conscience in general, which makes them nervous and jittery altogether, or are emotionally over-reactive. Such people show considerable physiological reactivity, even after irrelevant questions, and might be considered to be lying if this fact were not taken into account. The answer pattern on the irrelevant question provides us for each subject with a base line indicative of his response  pattern when he is speaking the truth; lying can be diagnosed only when marked difference from the normal response pattern are apparent in connexion with relevant questions.

Another safeguard which should always be employed is that no single response  is taken as evidence of lying. T he same question or a similar one, should always be asked several times, and only if there is considerable consistency in the subject’s response pattern indicating his guilt should this be regarded as suggestive. This is a very important safeguard indeed. Accidental factors, such as a sudden cramp, a sneeze, or a sudden loud noise, may produce effects indistinguishable from the emotional concomitants of lying, and these irrelevant factors can only be excluded by repeating the whole procedure several times.

In certain circumstances a rather different form of questioning  can be used , which has great advantages. This has been called the ‘ peak of tension’, or ‘guilty knowledge’ technique, and is dependent for its usefulness on the fact that a guilty person may possess knowledge which no innocent person would have. Any question regarding this knowledge, or any reference to it , would produce emotional reactions in the guilty person which would not be present in an innocent one.

In some cases the type of physiological reaction used was not one of those mentioned so far, but the so- called PSYCHOGALVANIC reflex. This is a rather mysterious phenomenon involving the measurement of the resistance of the skin to the passage of an electric current. Electrodes are fixed to the palm and the back of the hand, and a current so slight as to be quite imperceptibles then set up. The resistance offered by the hand to the passage of this current  is measured, and it has been universally found that any sudden shock or emotion produces a characteristic fall in this resistance. This fall occurs after a latency period of about a second or so after the stimulus has been applied and  appears to be proportional, roughly , to the amount of disturbance caused. There is no universally accepted explanation of this phenomenon, although there is some reason to believe that it is connected with the activity of the sweat glands of the hand. Emotion is known to produce activity in these sweat-glands, and sweat, being salty, is good conductor of electricity. However this is hardly the whole explanation and other possibilities have still to be considered. Fortunately, the usefulness of this method of registering emotion does not depend  entirely on a knowledge of the mechanisms which produce it and, in certain circumstances , the psycho galvanic  reflex is a better indicator of deception than any of those referred previously.

Other factors are more difficult to deal with Mental deficiency, for instance, make a subject almost useless for a lie-detector test. A very stupid person, who may not be able to distinguish between truth and falsehood or understand the social obligation of telling the truth, or who has no fear of detection, will not give useful results which can be interoperated in any way. Much the same is true  for young children, who are not fit subjects for lie-detector tests. Obviously innocent persons frequently give records so abnormal and erratic that no interpretation is possible.

Much greater difficulties are caused by certain people who are relatively unresponsive  to the conditions of testing. A person who refuses to believe in the efficacy of the test and who therefore  is not worried at all about giving himself away, will tend to show less emotion when telling a lie and therefore produce less easily interpretable records on the polygraph. Some people show a quite extreme absence of emotion, and such people, while actually guilty, might easily be pronounced innocent in terms of their reaction in the lie-detection test. Again some people are able to control their mental associations and processes sufficiently to avoid give-away responses. Fortunately  only few people seem to be able to control their minds to the extent required in order to ‘ beat the machine ‘ but it should be remembered that some people do possess this ability , and that their number seems to be particularly large among hardened criminals .

Among persons knowing the psychological basis of the lie detector, other tricks may sometimes be employed to make detection impossible. It will be remembered that lie detection depends very much on a comparison between items which are relevant and items which are irrelevant. If the subject is capable of causing physiological reactions to irrelevant items , then the comparison  will become useless and the record will not be capable of revealing damaging information. Causing physiological responses to innocent items may be done in various ways. For example a person stepping on his left foot with the heel of his shoe, resulting pain producing a reaction sufficiently like those  of lying to make the record unusable. Other people have been known to indulge in sexual fantasies when answering innocent questions, thus producing physiological responses to the fantasies which the investigator would attribute to the next question. It is not categorically  possible to say that such tricks may not work occasionally , but in most cases the experienced examiner will notice what the accused person is doing and will draw his own conclusions.

What are the main changes which are indicative of deception ? The most reliable index is  a simultaneous occurrence of a suppression in respiration and an increase in blood pressure immediately after the subject answer. However, even if only one of these two  reactions occurs it is a fairly safe guide to the examiner. Occasionally, deception may be indicated by a decrease in blood pressure, occurring several seconds after the subject has made his untruthful reply to the question. Heavier breathing 15 to 20 seconds after a reply to a relevant question has been given is also frequently indicative of lying; it is the physiological concomitant of a feeling of relief that this dangerous point has been passed with apparent safety, and it may  also occur at the end of the questioning period when the subject is told that he will not be asked any more questions. A last deception criterion is a slowing up of a subject’s pulse-beat immediately after his reply to a question.

In addition, the lie-detection techniques at present in use have not been adequately standardized with respect to instrumentation, the manner in which a test should be conducted, the interpretation of recordings, or the training of competent examiners. In such circumstances, incompetent or dishonest persons might represent themselves as ‘lie-detector experts’ and give inaccurate or perjured testimony.