The Polygraph Technique

THE POLYGRAPH TECHNIQUE

• Polygraph Examination is generally used as an investigative aid/technical aid in the investigative process.
• Ultimate Objective of Conducting Polygraph Examination is to obtain the subject’s admission or confession to the offense committed.
• Admission is a statement of fact by the accused, which does not directly involve an acknowledgment of guilt in committing or having participated in the commission of an offense.
• Confession is a declaration made by a person voluntarily, stating or acknowledging that he has committed or participated in the commission of a crime.

Tripod Foundations of Polygraph Technique

• 1. The Mechanical Basic Premise – The polygraph machine is mechanically capable of making graphical records containing reliable information regarding physiological changes.
• 2. The Physiological Basic Premise – Among the physiological changes that may be recorded and identified are those that automatically occur only following the stimulation of specific nervous system components; it can be reliably diagnosed.
• 3. The Psychological Basic Premise – Under the polygraph premise, the specific nervous system component whose stimulation can thus be diagnosed is reflected by the involuntary mental and emotional processes of the individual who is consciously attempting concealment of deception.

Physiological Phenomena as Basis of Detecting Deception

• 1. Blood Pressure and Heartbeat Frequency – Blood Pressure Increase and Heartbeat Frequency following relevant questions and the suppression in breathing are the criteria for detecting deception.

• Ink Curves on the heartbeat recorded on a moving graph paper of a polygraph represent the beat frequency (pulse) and the two pressures: Systolic (High Pressure) and Diastolic (Low Pressure).

• The Heart is an automatic organ that continues to beat even when removed from the body or provided with proper blood.

• The rate and force of the heartbeat are regulated by two sets of nerves:

  • The Sympathetic Set – accelerates the beat.
  • The Cranial Autonomic System – retards the beat.

• It is also known as Adrenaline – a hormone that increases the heartbeat frequency.

• 2. Breathing as a means of Detecting Deception – Breathing consists of two steps: Inspiration (Inhalation) and Expiration (Exhalation).

• 3. Electro-dermal Response – The skin changes resistance electrically upon the application of certain external stimuli. It consists of two categories: Normal and Abnormal Response.

  • Examples of Abnormal Responses:
  • 1. Machine Fright Response – it appears on the first question or so and no longer appears throughout the test.
  • 2. Physical Movement Response – causes physiological (muscle) changes to take place within the body that shows up electrodermal response.
  • 3. Outside Interference Response – any unusual noise (e.g. cough/sneeze) to which the subject is not accustomed at the location, will usually produce it.

• 4. Mental Tie-up Response – another name is a guilt complex.

• 5. Deception Response – abnormalities as a result of telling a lie.

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Polygraph Technique Accuracy

• Current polygraph research indicates that when a specific single-issue polygraph exam is conducted by a qualified and competent polygraph examiner and is properly administered the accuracy rate is between 95\% \text{ to } 98\%.
• The accuracy of the polygraph results is high depending upon the factors that affect it.
• Factors that Affect the Accuracy of the Polygraph Results:
  1. The instrument
  2. The condition of the subject
  3. The condition of the examination room
  4. The qualification and skills of the examiner
• Specifically, the 15\% errors of lie detection test come from the following circumstances:
  1. Nervousness or extreme emotional tension experienced by a subject who is telling the truth regarding the offense in question but who is nevertheless affected by apprehension induced by the mere fact that suspicion or accusation has been directed against him/her, etc.
  2. Physiological Abnormalities such as excessively high or excessively low blood pressure, diseases of the heart and respiratory order.
  3. Mental Abnormalities such as feeblemindedness as in idiots, imbeciles, and morons, etc.
  4. Unresponsiveness in a lying or guilty subject because of no fear of detection, etc.
  5. Attempt to “beat the machine” by controlled breathing or by muscular flexing.
  6. Unobserved application of muscular pressure which produces ambiguities and misleading indications in the blood pressure tracing.

Limitations of the Polygraph Technique

• 1. It is an invaluable investigative aid, but never a substitute for investigation.
• 2. It is not a lie detector but only a scientific diagnostic instrument.
• 3. It does not determine facts, it records responses to that which the subject knows to be true.
• 4. It is only as accurate as the examiner is competent.
• 5. The test will not be given until enough facts have been established to permit the examiner to prepare a complete set of suitable questions.
• 6. The test will not be given without the voluntary consent of the subject.
• 7. No indication will be given to any person or placed in any report that a person will be considered guilty because he refused to take the test.
• 8. A test will not be given until the accusations have been explained with the subject.
• 9. No attempt to use polygraph for mental or physical evaluation of any person.
• 10. No examination will be conducted on an unfit subject.

Barriers to the Polygraph Examination

• There are instances where it is impossible to make an analysis of polygraph tests because of the following:
  • Pathological Liar
  • Mental Cases

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• Prepared by: Prof. Aleah F. Macasaet, RCrim, LPT, DM, (Ph.D. CAR) CCJ Faculty