Lie Detectors

1
Lie Detectors

• What do they really detect?

By Laura Malone
2
From the beginning of time

• China- chew and spit out rice powder
• England swallow trial piece of cheese and
  bread
• India- magic donkey tail

3
History of Polygraphs

• Cesar Lombroso (1885) measure blood pressure with
  hydrosphygmograph

4
History of Polygraphs cont

• 1914 Benussi designed machine to measure
  breathing rate
• 1915 Marston used sphygmomanometer to monitor
  blood pressure and experimented with galvanometer
• 1930s Leonarde Keeler designed the modern
  polygraph machine tracks perspiration, blood
  pressure, heart rate, and respiration

5
Output of Polygraph
6
Blood Pressure Block Diagram
7
Respiration Block Diagram
8
Perspiration Block Diagram
9
Heart Rate Block Diagram
10
Computer Voice Stress Analyzer (CVSA)

• New method of determining truthfulness
• Micro tremors found in the muscle when it
  contracts
• Minute oscillations have a frequency between 8
  and 12 Hertz

11
CVSA Block Diagram
12
CVSA vs. Standard Polygraph

• CVSA isnt restricted to yes or no answers?
  can pick apart lies in sentences
• Proposed that CVSA wont affect the results
• CVSA cost 10,000
• With training 13,000
• Polygraph cost 6,000
• With training 25,000
• Polygraph measures four physiological responses
  instead of just one

13
Ethical Issues

• No final decision on Federal Level
• On State Level, decisions made on case-by-case
  basis
• 1988 Employee Polygraph Protection Act
• Private employers cant require polygraph exam to
  employee
• Does not protect government officials