POLYGRAP
H
Guided By :
Prof. Vidita Tilva
Prepared By :
Paxaj Shukla (12BIC056)
Aasheesh Tandon (12BIC044)
WHAT IS A POLYGRAPH?
• A polygraph, often called a “Lie Detector,” is a
machine that measures human responses to
questions...
A BRIEF HISTORY
• William Moulton Marston : creator of the systolic
blood pressure test - one component of the modern
poly...
HOW DOES IT WORK ?
• Polygraph machine records multiple signals
using 4 to 6 sensors attached to the patient’s
body. The s...
HOW DOES IT WORK ?
 The Nervous System reacts to different situations
differently.
For this, it uses different parts of i...
THE INSTRUMENTATION
• Cardio – Sphygmograph : collects blood pressure and
heart rate data
• Pneumograph : measures respira...
ADMINISTRATION OF THE TEST
• Familiarizing the subject with the test
• Pre-test Interview
• Formulating Questions
• Analys...
TYPICAL QUESTIONNAIRE
The Relevant – Irrelevant Test
Comparison Question (Control Question) Test
Reid Comparison Questi...
ACCURACY
• U.S. Attorney General John Ashcroft concedes that
polygraphs used in federal agencies have an error rate
of abo...
Polygraph presentation
Polygraph presentation
Polygraph presentation
of 12

Polygraph presentation

How polygraph works? Accuracy? Questionnaire? Instruments used?
Published on: Mar 4, 2016
Published in: Education      
Source: www.slideshare.net


Transcripts - Polygraph presentation

  • 1. POLYGRAP H Guided By : Prof. Vidita Tilva Prepared By : Paxaj Shukla (12BIC056) Aasheesh Tandon (12BIC044)
  • 2. WHAT IS A POLYGRAPH? • A polygraph, often called a “Lie Detector,” is a machine that measures human responses to questions, measuring a lot of physiological symptoms of anxiety or emotion to estimate if the subject is being truthful or not.
  • 3. A BRIEF HISTORY • William Moulton Marston : creator of the systolic blood pressure test - one component of the modern polygraph. • John Augustus Larson : first American police officer to use polygraph in criminal investigations. • Leonarde Keeler : was the co-inventor of the polygraph. John Augustus LarsonWilliam Moulton Leonarde Keeler
  • 4. HOW DOES IT WORK ? • Polygraph machine records multiple signals using 4 to 6 sensors attached to the patient’s body. The sensors usually record: • The person's breathing rate • The person's pulse • The person's blood pressure • The person's perspiration
  • 5. HOW DOES IT WORK ?  The Nervous System reacts to different situations differently. For this, it uses different parts of it, namely : I. Somatic Nervous System II. Autonomic Nervous System a) Sympathetic Nervous System b) Parasympathetic Nervous System Arousal  Increased ANS activity  Lie
  • 6. THE INSTRUMENTATION • Cardio – Sphygmograph : collects blood pressure and heart rate data • Pneumograph : measures respiratory patterns • Galvanograph : measures electro-dermal activity or sweat
  • 7. ADMINISTRATION OF THE TEST • Familiarizing the subject with the test • Pre-test Interview • Formulating Questions • Analysis of the result
  • 8. TYPICAL QUESTIONNAIRE The Relevant – Irrelevant Test Comparison Question (Control Question) Test Reid Comparison Question Test Zone Comparison Test Concealed Information Test Peak-of-tension Test
  • 9. ACCURACY • U.S. Attorney General John Ashcroft concedes that polygraphs used in federal agencies have an error rate of about 15% . Some critics even assert that credible scientific research has found that commonly used polygraphs have error rates of 40% or more, only slightly better than flipping a coin to decide if a subject is lying . • A truth-teller might recognize that a question has significance in the investigation and exhibit the same increased cardiovascular and sweat activity as a liar. This innocent subject may be wrongly accused of lying, with very serious and unjust consequences. • Some people, such as spies, are trained to disguise their feelings, can lie very naturally, and can easily pass polygraph tests.