LIE DETECTION AND INTERROGATION TEST PROCEDURE AND DIAGOSTIC TECHNIQUE Prof. Allan I. Tillain, M.S. CRIM. 1. Definition of Terms 1.1. Admission- is a statement of facts, partial acknowledgement of guilt and usually given with some justification or exemption in admitting. 1.2. Confession- direct acknowledgement of guilt or a statement of guilt. 1.3. Deception- is the act of deceiving or misleading usually accompanied by lying. 1.4. Diastolic blood pressure- refers to the downward blood pressure representing the low pressure to the closing of the valves and heart relaxed. 1.5. Diacrotic notch- refers to the short horizontal notch in a cardio-tracing located at the middle of the diastolic stem. 1.6. Electro dermal response- it refers to human body phenomenon in which the skin changes resistance electrically upon the application of certain external stimuli. Also referred to a Psycho galvanic skin reflex or galvanic skin response. 1.7. Emotion- it refers to an emotion response to specific danger that appears to be beyond a person’s defensive power. 1.8. Environment- is the sum total of the dissimulation that a person acquired from the time he was conceived and his exposure to his surroundings. 1.9. Heredity- is the transmission of physical and mental traits of the parents to their offspring through the genes.
1.10.Interview- simple questioning of one who is willing and cooperative. 1.11.Interrogation- forceful questioning of one who is reluctant to divulge information. 1.12.Lying- is the act of uttering or conveying falsehood or creating a false or misleading impression with the intention of affecting wrongfully 1.13.Normal response- refers to any activity or inhibition of a previous activity of an organism or part of the organism resulting from stimulation. 1.14.Ordeal- refers to the oldest form of crime detection done by subjecting a subject to an obstacle or trial and sometimes even involving third degree. 1.15.Polygraph machine- is a sensitive machine which is likened or compared to an X-ray, which requires proper interpretation for validation and its accuracy is said to be directly proportional to the knowledge, skills, education, desire, competency and integrity of the operator. Hence, the attitude of “let’s put them on the lie box” should be firmly discouraged. 1.16.Specific response- refers to the response given by the subject which considered a deviation from the normal tracing or norms of the subject. 1.17.Stimulus- refers to any force or motion coming from the environment and which reach an organism has the tendency to arouse. 1.18.Systolic Blood pressure- the upward blood pressure as the apex of the curve caused by the contraction of the heart, valves are open and blood is rushing into the arteries. 2.
Nature of Polygraph - Polygraph is an instrument that is used for instrumental interrogation, it does not and cannot detect lies, and it is incapable of drawing or reporting any conclusion. It is constructed and designed to assist a qualified examiner in arriving a diagnostic opinion.
- The term POLYGRAPH literally means, Multiple writings”, and is now often connected to the term “lie detector”. It is an instrument for recording several pulsations (as of physiological variables) simultaneously. - What comes out of polygraph examiner’s mind is a supposition of diagnostic opinion. The value of polygraph is directly proportionate to the training and skills of the examiner. An examiner is a fallible human being subject to error. We must concede that the examiner can be wrong. 3. Legal Status of Polygraph - In U.S v.s Frye, which was known to be the first case in lie detection, the Supreme Court in 1923 decided it was not admissible in evidence. - The United States Court of Appeals, Eleventh Circuit (by vote of 8 Justices and 4 against) has reverse the 1923 ban on polygraph evidence and opened the door to the administration of the result of the polygraph tests. - The decision in U.S v.s Picciononna discards Frye as a rule, and sets procedure and limits on polygraph test admissibility. The decision does not limit the Trail Court’s discretion to exclude polygraph evidence. The Court outlined two instances where polygraph evidence can be admitted. First, there must be stipulation between two parties. Second, when it is used to impeached or corroborate the testimony of a trial witness, the court further cited that the administrator of the test must be trained ad have better equipment for accuracy. - In the Philippines, our Court do not admit polygraph evidence as it will take place of the judge. Besides, a party cannot cross-examine the polygraph machine. 4. Development of the Polygraph 4.1. Cardiosphygmograph a. Cesare Lombroso (1895) – Credited to be the first to conceive the idea of utilizing scientific lie detection. b. Angelo Mosso (1895) – Utilized a scientific cradle and focus on the importance of fear as a strong influence to deception. c. William M. Marston (1915) – He made used of a sphygmomanometer and focus on the importance of the Systolic Blood Pressure. He also devised the discontinuous technique in questioning. d. John A. Larson (1921) – Devised the so-called “Bread lie Detector”, a scientific instrument capable of simultaneously recording changes in blood pressure, pulse beat and respiration. 4.2. Galvanograph a. Sticker- works on the galvanograph component and study the influence of the sweet glands to skin resistance. b. Veraguth- formulated the term Psycho-galvanic skin reflex following the study of sticker. c. Richard O. Arthur- The person who developed a polygraph machine with two galvanic skin resistance. 4.3. Pnemograph a. Vittorio Bennussi- Focus in the formulation of the Inhalation and Exhalation ratio. b. Harold Burtt- Considered respiration as a week basis in determining deception and incorporate the systolic blood pressure to respiration. 4.4. Keymograpgh a. Leonarde Keeler- Developed the kymograph machine and the Keeler’s Polygraph in the year 1926 as one of the great advancement to the development of the polygraph machine.
5. Other Considerations 5.1. Thomas Jefferson- first man to used the word “polygraph” 5.2. John E. Reid- developed the Reid Polygraph with an incorporation of muscular resistance compare to the Keelers and the Stoelting. Also developed the SAT test and Control Question Test. 5.3. Francis Galton- formulated the Word Association Test. 5.4. Cleve Backster- formulated the Numerical Scoring on the Polygraph chart and standardizing quantitative polygraph technique. 5.5. Sir James Mackenzie- a heart specialist who published in two British journal the machine he used in his work and named it “Ink Polygraph” 5.6. Ayur Vida- a hindu book of science and health around 500 B.C Considered as an earliest known reference to a method of detecting deception. 6. Scientific Methods of Detecting Deception 6.1. Polygraph test - Aid and not a substitute or replacement for investigation. - Not admissible in court to prove the guilt of the subject. - Cannot be conducted if insufficient amount of information were gathered. - Minors, mentally-ill or retarded are exempted. - Cannot be conducted to unfit subject. - Polygraph machine is not a lie detector machine. - The accuracy of the machine is directly proportion to the credibility of the examiner. - Cannot be used for diagnostic purposes. 6.2. Use of Alcoholic Beverages - The subject is made to drink hard liquor in such a mount that would him lose control or inhibitions. - Information gathered through this method is not admissible in court. 6.3. Narco-Analysis Test/Administration of Truth Serum - Use of narcotic or anaesthetic drug. - Drugs injected hypodermically or intravenously - Dangerous and not admissible. 6.4. Word Assciation Test - Group of words, objects or photographs will be presented - Time pressure - This was first devised by F. Galton in 1870 and later was modified and improved by others such as Munsterberg, Orosland, Luria and Jung. - In the Galton’s technique there are two main criteria for detecting indications of deception and these are: (1) Incriminating answer words, and (2) Delayed answer 6.5. Use of Hypnotism - Information gathered through this method is also not admissible in court. 7. The Tripod Foundation of Polygraph 7.1. Mechanical leg basis premise - The polygraph machine is mechanically capable of making a graphic record containing reliable information regarding physiological changes. 7.2. Physiological leg basis premise
- Among the physiological changes that may be recorded and identified are those that automatically occur only following the stimulation of specific nervous component system and from which the stimulation of those specific nervous system component that can be reliably diagnosed. 7.3. Psychological leg basis premise - Under this premise, the specific nervous system component whose stimulation can thus be diagnosed are so stimulated by the involuntary and emotional processes of the individual who is continuously attempting him to believe that exposure to deception is quite possible although undesirable. 8. The Different Parts of Polygraph It is divided into five sections: 8.1. KYMOGRAPH SECION or CHART DRIVING MECHANISM 8.1.1. Function: to move the chart paper at a uniform rate of speed under the pens - The chart roll arbor- this holds the chart roll and fits into V-shape along with the spring to hold it in placed. - Idler roller- it rolls with the paper to prevent the friction - Pen table- flat portion where the pen write on the chart - Sprocket roller- is a roller that fit into perforated edges of the chart paper - Cutter bar- used to cut the paper at the end of the test - Off or On power switch - Synchronous motor- to run the chart paper at the uniform rate speed regardless of the voltage change. 8.1.2. Chart Paper There is approximately 100ft of paper to a roll and there is a narrow green line on the chart paper about 6 ft. from the end of the roll to indicate the end. 8.2. PEN AND INKING 8.2.1. Function: This is used to record the test permanently - The lowest pen is the cardiosphyograph pen - The center is the galvanograph pen, which is also the longest pen and - The top two pens are the pnemograph pens 8.3. PNEUMO SECTION 8.3.1. Function: To record the thoracic and abdominal of the subject The convoluted rubber tubes, which are ten inches long, are place over chest and abdomen of the subject. 8.4. CARDIO SECTION 8.4.1. Function: To record the galvanic skin response (electro dermal response) or the degree of the subject’s sweatness. Two small metal plates called as the “galvanometers”are connected to the subject’s fingers (normally the middle section of the index and ring of the left hand). These plates record the filling up of sweat glands (empty during homeostatic condition) and nearly immediate reabsorption of the moisture. 9. THE POLYGRAPH EXAMINATION 9.1. The typical polygraph examination consists of three distinctive parts: 9.1.1. THE PRE-TEST INTERVIEW - This includes all considerations bearing on examination up to the time of actual activation of the examination. Most people do not really realize that in fact, the most important and often the longest phase in a polygraph examination is the pre-test interview. The pre-test interview can absorb 45 minutes in general. - During the pre-test interview the examiner will: a. Talk to the subject ad do his best to put him/her at ease
b. Will give the subject a detailed explanation of what is going on to happen during the actual testing phase and confirm his understanding. c. Will define subject’s legal rights. i. The right to remain silent ii. The right to have an independent counsel preferably of his own choice iii. The right against self-incrimination d. Briefly explain to the subject what the polygraph is all about and how it works. e. Write down all the subject’s details in order to make the identification sheet attached to the report. f. Ask certain questions about the subject’s health, if he has eaten over the last 5-6 hours, if he has a good night sleep and is not tired. g. Talk about the incident or issue. h. Discuss all the questions, which will be asked, and make sure the subject answers them all confidently, and understandingly. i. Ask the subject one last time if he is prepared to undergo the test and then invite him to take a seat in the interviewing chair. j. The examiner will then connect the different components to the subject while asking him to sit absolutely still during the whole time of each chart recording (approximately 4 to 5 minutes) k. Test execution or questioning phase (actual examination or chart collection phase) l. Post-test or diagnostic phase 9.1.2. TEST EXECUTION OR QUESTIONING PHASE (The Actual polygraph examination) - All considerations bearing on polygraph examination from the time the instrument is placed on the subject until the instrument is deactivated. - Before the pre-test interview, the examiner had a briefing with the client, which will typically the investigator, but in certain cases, can be the subject himself. - During this briefing, the examiner has to make up his mind as to which type of questionnaire he will be using Depending on the type of test he will draw up a specific questionnaire, discuss the relevant questions with the client, on his approval go to the interview room. THE INTERVIEW ROOM - The ideal interview room is not too big, not too small (3.5 x 3m) It should be guaranteed have privacy with, no possibility of interference (no telephone). The furniture has to be sober but adequate; desk and chair of examiner, normal chair for the subject, and a chair for the test itself, this last chair has to be really comfortable, has to have large enough arm rests in order to give the subject the easiest means to sit still during the chart recording. Psychological research has indicated that the most relaxing color for the walls is with a very light hint of purple mix. This color seems to subdue the subject and leads easier to confessions. 9.1.3. POST TEST OR DIAGNOSTIC PHASE - All consideration that bear polygraph examination from the time the instrument is deactivated falling final polygram until examiner’s diagnostic opinion is reported to proper authorities and the case is concluded. 10. QUESTION TYPES
In different types of test questionnaires, three different types of questions will be used. 10.1. Irrelevant Questions - Is a question from information about the subject will not normally lie, which does not pertains to the matter under investigation and to which the examiner knows or can reasonably ifer the answer. - These are essentially questions, which all give the examiner a truthful answer. - It is generally a “Yes” answer. 10.1.1. Uses - To reduce subject’s excitement level. - To assist in returning tracing to or toward proper baseline in preference to mechanical adjustment. - To serve as an interpretation to specific reaction by comparison. - To conserve the subject’s ability to react 10.1.2. Examples of irrelevant questions Have you ever been married_________? Is today _______? Did you ever smoke__________? Is your name_______? Are you sitting on a chair _______? Have you ever been called ________? Are you a citizen of ___________? Where you born in ______? Are you ________years old? Do you think_______? Have you take anything to eat today________? NOTE: The irrelevant question gives the examiner a walls 10.1.13. Caution in the used irrelevant questions: a. Some irrelevant questions may under certain circumstances become relevant to your subject b.Example-of irrelevant question which may cause subject responses. a. Smoking- responses against doctor’s, parents. Objection, against situation, against religion. b. Married- Separated, bigamy, polygamy, cheating, common-law, pregnancy, incompatibility, shotgun wedding, desertion, homosexuality, pre-marital sexual relation. c. Name- an alias, nickname, dislike, mispronunciation. d. Age- Sensitivity, uncertainty etc. c. Question that can develop reflective reaction- about religion, race d.Question about condition subject to change- about weather. 10.2. Relevant questions - Is a question formulated from information pertaining to the object of examination and to determine the subject’s knowledge or complicity and/or truthfulness or deception regarding the issue in question. - The relevant questions are the questions of which the examiner wants a result. These are the questions which the subjects know the truth about and is the reason for undergoing the test. The question must be phrase to engage the subject to say “no”. If for example we want to solve a dispute between X and Y, where X says she gave Y a check and X says she never got it and we will ask X: “Did you give Y the check we discussed?” He will obviously say, “yes” while we want “no”. - The examiner wil retract a “no”answer by formulating the question as follows: “Did you lie when you told me you gave Y the check we discussed?” Now we got a “no” answer.
- The relevant questions are split up in four categories (e.g. Carnapping) a. Primary involvement: Did you steal the car? b. Secondary involvement: Did you help anybody to steal the car? c. Guilty Knowledge: Do you know who stole the car? d. Evidence connecting: Did you get any reward coming from the stealing of the car? Or Do you know where the car is at present? - These four different questions are called “the four legs of the crime”. Did you do it. Did you help, do you know who did it, and did you get anything out of it? 10.2.1. Formulation of relevant questions a. Inquire from pertinent information’s related to the matter being investigated. b. Point if determining whether or not deception is attempted. c. As a short and precise as possible. d. Subject’s own language should be used whenever possible. e. All questions must lead themselves to being answered “yes” or “no. f. Selection of words: - It is desirable to substitute word with a softer connotation. - There is a possibility that subject’s interpretation of words used might caused him to produce a misleading response. g.Larceny- take , took, steal, forget to return h.Homicide- kill, shoot, hurt, take life and the like i. Rape- molest, attack, assault, finger, screw etc. 10.2.2. Questions to avoid: a.Double meaning question b.Did you steal the gun and fired it? c. Did you steal the money and the jewelleries? d.Did you rape and kill the victim? 10.2.3. Questions in the form of accusations a.Did you use the knife when you killed Bert? b.Were you alone when you broke in to the house? c. You killed Nida, didn’t you? 10.3. Control questions - These are questions on which all subjects will be potentially untruthful. They are used to absorb any anxiety of a truthful subject and draw attention away from the relevant questions. The control questions are so designed that they will draw a possible lie from the subject to items broadly similar to the issue on hand. - The reaction to the control questions will be compared to the relevant questions to give a result. 10.3.1. Examples: - Before this year, did you ever steal anything in your life? - Before this year, did you ever lie to someone who trusted you? - Do you remember if you ever stole anything from a place where you work? - Do you remember seriously lying to any of your colleagues? - (The question is typically a “no” question) 11. TYPES OF TEST 11.1. General Question Test
- Consist of series of relevant and irrelevant questions in a planned order. 11.2.
Peak of Tension Test - Consist of only one relevant and a series or irrelevant questions. - Resemble, in every general way, the card test, for it consist essentially of the asking of a series of question in which only one has any bearing upon the matter under investigation - Padding questions before the after the relevant questions.
11.3.
Card Test - The subject is presented with seven (7) previously numbered cards face down. - He will be instructed to take one, look at it and return it with the rest of the
cards. - The examiner will shuffle the cards an each card will be shown to him, with the instruction that he will answer “NO” to all cards, even if the one being shown to him is the one he has seen earlier. 11.4.
Guilt complex test - Used primarily for overly responsive subjects - A totally fictitious incident but a similar nature to the matter being investigated and make him believe it is real - The purpose is to compare the response with those response made concerning the actual under investigation
11.5.
Silent Answer Test - Subject in instructed not to give any verbal answer, the subject will only answer mind Yes Test No Test Guilt Complex Test Mixed Test - Consist essentially of an arrangement of the first and third test questioned. - Administered response on earlier test or to compare the degree of reaction between relevant and control questions.
in his 11.6. 11.7. 11.8. 11.9.
12. QUESTION FORMULATION 12.1. Case Sample: Qualified Theft Irrelevant question
1. Have you ever been called _______? 2. Do you know that today is _______?
Relevant
3. Regarding the missing P5000.00 cash inside your office at the FEBTC Palanca branch last Oct. 15, 2004, do you have anything to do with?
(Weak Relevant)
Irrelevant question
4. Are you sitting down now?
Relevant (Strong)
5. Were you the one who stole the missing P5000.00 cash inside your office at FEBTC Palanca branch last Oct. 15, 2004?
Control (Primary Control) 6. Before reaching the age of_______, have you ever stolen anything? Irrelevant question Guilt Complex Question
7. Are you a bank employee? 8. Were you benefited in any manner with the loss of P5000.00 (Evidence Control Question) cash inside your office last Oct. 15, 2004? Relevant (Knowledge question)
9. Do you know for sure who stole the missing P5000.00 cash inside your office last Oct. 15, 2004?
Irrelevant
10. Have you ever stolen anything from your past employment? (Secondary Control Question) 13. THE FOUR (4) GENERAL TYPES OF TRACING SEGMENTS 13.1. Average tracing segment A segment that shows no physiological evidence in the emotional level within the stress area on the polygraph chart or polygrams. 13.2.
Reaction tracing segment A segment within tracing that shows physiological evidence that the sympathetic division of the autonomic nervous system has become active indicating a physiological change in the subject’s emotional level.
13.3.
Relief tracing segment A segment within tracing that shows physiological evidence that the parasympathetic division of the autonomic nervous system has become active following the stress area on the polygraph chart indicating a physiological return to the subject’s exhibited average emotional level.
13.4.
Distortion tracing segment A segment within tracing that departs from the average emotional level but lacks physiological evidence of either sympathetic or parasympathetic activation within the stress area on the polygraph chart indicating a lack in physiological origin.
14. RULES IN INTERPRETTING REACTIONS: a. If the control question responses (6 & 10) are greater than the responses to the questions (3, 5, 9) about the principal offense being investigated, the subject is telling the truth. b. If the responses on the principal test questions (3, 5, & 9) are greater than the control questions (6 & 0), subject is telling a lie. c. Where there is no appreciable difference between the control questions (6 & 10) and the principal offense question responses (3, 5 and 9 ) there is specific response in (8), subject is telling the truth. d. Where the is no specific response on principal offense questions (3,5 & 9) and no response on (8) subject is lying. 15. CHART MARKINGS , SYMBOLS AND SIGNS
Beginning -------------------------X Laugh------------------------------L Yes-------------------------------- (+) Paper Jump-----------------------PJ No--------------------------------- (-) Ending------------------------------XX Coughing--------------------------C Movement-------------------------M Clear throat-----------------------CT Sigh---------------------------------S Sniff--------------------------------SN Burp--------------------------------B Yawn-------------------------------Y 16. THE AUTONOMIC NERVOUS SYSTEM AND THE MODERN POLYGRAPH INSTRUMENT - Man in his earliest development was endowed with a sophisticated survival mechanism or an emergency system of nerves that automatically prepares his body to meet situations that threated his well being - His health and survival depends on the maintenance of stable fluids and chemical balance in all vital organs of his body despite the drastic changes in the environment about him, and this balance was termed as homeostasis (refers to the action taken by an individual to protect or to restore certain favourable states of equilibrium). -In the center of the brain is a gland called Hypothalamus; our internal regulator. - All our unconscious activities such as sleep, digestion, pulse, blood volume and respiration are being controlled by the Autonomic Nervous System, manipulated by the hypothalamus. - When our well-being is threatened, either physically or psychologically, one of our sensors such as hearing, seeing, feeling, or even instinct, will send alarm signals to the autonomic nervous system which will activate the sympathetic department and take action. - In polygraph test, the receptor is the ear of the subject, which receives the threatening question or stimulus from the polygraphist. - The stimulus is transmitted from the ear via sensory neurons into the brain where the hypothalamus will analyse, evaluates, and resolves that particular question. It makes a decision for the subject as to whether it is threatening or not threatening situation. If the question perceived as threatening, the hypothalamus immediately activates the sympathetic division of the autonomic nervous system. - When the sympathetic is activated, it immediately prepares the body for “fight or flight” by causing the adrenal glands to secrete hormones known as epinephrine and norepinephrine so that the blood will be distributed to those areas of the body where it is most needed to meet the emergency, such as brain and larger group of muscles. The norepinephrine causes the arterioles in certain parts of the body to constrict; thereby preventing blood from entering to those areas where it is not immediately needed. While the sympathetic system organized this whole defense system in next to no time, the parasympathetic system, functionally antagonistic towards his partner, follows in order to re-establish the chemical balance of the body. Without these two antagonistic partners, the defense system of the body will go into a high build up and cause damage to the body (e.g. burst artery in the brain). - The two items are essential to maintain a perfect homeostasis. 16.1.
Other very obvious effects will take place known by all of us: - The mouth gets dry, due to salivary glands producing much thicker saliva
-
17.
The heart pumps faster, thereby increasing blood volume and pulse Stimulation f the respiratory muscles leads to breathing changes The sweat glands are stimulated and forced to release perspiration The iris of the eye dilates, permitting more light into the eye. Involuntary muscles contract.
COMPARISON OF PSYCHOLOGICAL STRESS EVALUATION TO POLYGRAPH IN EVALUATING TRUTH OR DECEPTION VOICE STRESS ANALYSIS 17.1.
Underlying principles - In 1964, Charles R. Mc Quiston made a new step in the truth verification research - The US army desired to obtain an alternative instrument to the polygraph with no need for direct connection to the subject’s body, one of the main disadvantages of polygraph. - The instrument was to be a “remote” lie detector with a concept based on recognition that emotional stress induces measurable change into the human voice. - All VSA’s rely on measuring strss-induced changes to the muscle micro tenor as displayed in involuntary changes in voice. - These changes can be found in a tremor associated with contraction of muscles, affecting minute oscillation at a frequency of about ten to twelve hertz cycles per second. - The amplitude of this oscillation is a fiftieth or less of that total contraction. - Although all muscles do exhibit this tremor, the voice stress analyser will oy take into regard those associated with the human voice. - Since our voice transmits these tremors at the same time as the occurrence of stress, the PSE can be used to anaylze a narrative conversation, a serious advantage over the traditional polygraph, where only carefully timed (25 sec. interval) question, with only strict yes or no answers, can be used. - The basic of the PSE comes down to Mc Quistons discovery that, under stress, these tremors disappear, when a person speaks, air as pushed from the lungs upward to the vocal cord. As a result, the vocal cords vibrate in the frequency mentioned above (the speaker’s main leading frequency). - The air keeps flowing upward to the mouth and goes through the tongue, teeth and lips, thereby creating the speech flow. - When a person lies, the amount of blood in the vocal cords drops as a stress, so, no tremor. In short, the VSA searches for the disappearance of the normal tremor in a voice due to stress. - This lack of tremor indicates lie. 17.2. The development of the VSA - Charles R. Mc Quiston coined the name “Voice Stress Analysis” and together with two retired friends, Wilson Ford and Allan Bell, he developed the first prototype of his Psychological stress evaluator (PSE) - In 1970 the three of them founded “Dektor counterintelligence and Security, Inc. This company brought the first PSE on the market and is still one of the biggest manufacturers and suppliers of the instrument. - This instrument, applying voice stress analysis, represented the first major advance since the introduction of the Kymograph in 1920 by Keeler ( a device that physically records motion or pressure)
- For over 20 years the PSE was dominant in stress analysis, until the Verimetrics system, another invention of Mc Quiston, appeared. - The verimetrics allowed the analytical process to take advantage of the newly developed personal computers to more conveniently and effectively produce charts - Shortly afterwards Charles Humble brought the Computer Voice Stress Analysis (CVSA) system on the market the major advantage of this system brought was of “real time” analysis. - The interview could now be committed directly to the instrument, without the need of an intermediate recording on magnetic tape. 17.3.
Advantages of VSA over the Polygraph - The VSA can be used as a remote truth verification tool. - No direct connection to the subject’s body. - Possibility to interview the subject over the telephone - Previously recorded conversation can be analysed later - Nor mail conversation using full phrases can be used - The subject can be held ignorant of the fact that he is interviewed that his answers will be analysed (in this case the recording nor the analysis can be used against him)
17.4.
Disadvantages - The VSA is a relatively young instrument using a techniques, which has not been as thoroughly evaluated as the psycho physiological data recorded by the polygraph. - The polygraph has been used for many decades and has been a study object of many universities and agencies all over the world. - There is no doubt that the future will still bring dramatic improvements and the faults will be documented. - The VSA analyses only one single item, namely the tremor in the voice while the polygraph as its name says, reads multiple items, thoracic and abdominal breathing, blood pulse, blood volume, galvanic skin response and movement - However, the frequency and amplitude modulations in the voice cover a broad spectrum.
17.5.
Reliability / Accuracy - No truth verification technique can claim to be 100% accurate - In the past, it was commonly agreed that the polygraph had a higher reliability in correctly indicating deception or truthfulness - According to Clifton Coetzee, a well-known polygraphist and voice stress analyst, states in his work ( Truth extraction; 200:74) that a skilled and well-trained operator will obtain the same results with polygraph as well as the CVSA - Several sources indicate reliability of the CVSA a higher that 91.1% - The effectiveness of a VSA test is based on the total system consisting of the hardware, the software, and most importantly, the analyst.
17.6.
Conclusion - It is the investigator’s duty to analyse his needs and weigh the advantages and disadvantages of the two system. - The VSA is quicker, more versatile, can be easily hidden and can perform an interview as well as an interrogation
- The polygraph is considered in general more researched and filed-tested.
