The Truth About Lie Detectors

Brittany Smith

May 1, 2006

• General Idea about polygraphs• Skepticism Issues • Polygraph Instrument• Polygraph Examiners• Exam Procedure• Countermeasures• Legalities of polygraphs• Video Clip

Overview

Photo courtesy Lafayette Instrument

An analog polygraph instrument

Most analog polygraphs are being replaced by digital

devices.

• Polygraphs (“lie detectors”) are instruments that monitor a person's physiological reactions. – These instruments do not detect lies; they can only detect

whether “deceptive behavior” is being displayed.

• Asked a question about a certain event or incident– Examiner monitors changes in heart rate, blood pressure,

respiratory rate, and electro-dermal activity (or sweatiness in fingers)

• Used in criminal investigations, by banks, CIA, FBI, other government agencies, pre-employment screening

General Idea

• Voodoo science: polygraphs are no more accurate at detecting lies than the flip of a coin

• Statement from American Civil Liberties Union (ACLU)– "Despite claims of the lie detector examiners, there is

no machine that can detect lies. The lie detector does not measure truth-telling; it measures changes in blood pressure, breath rate and perspiration rate, but those physiological changes can be triggered by a wide range of emotions."

• Polygraphs can detect deceptive behavior even through the stress brought on by the exam itself

Skepticism

• Analog Digital computer polygraphs• Examiner = Forensic Psychophysiologist (FP)

Instrument*

Photo courtesy Lafayette Instrument

Today, most polygraph exams are administered with digital

equipment like this.

Photo courtesy Lafayette Instrument

Parts of a polygraph that monitor physiological

responses

• People in exam room: polygraph examiner, subject being tested

• Tasks of examiner, or FP:– Setting up the polygraph and preparing the subject

being tested – Asking questions – Profiling the test subject

– Analyzing and evaluating test data • Presentation of questions

– Cultural or religious beliefs considered

– Some topics may, by their mere mention, cause a specific reaction in the test subject that could be misconstrued as deceptive behavior.

Examiners

• 3,500 examiners in U.S.– 2,000 of above belong to professional organizations

• Polygraph licensing vary from state to state

– No government or private entity that controls polygraph licensing

• Axciton International Academy

– Accredited by the American Polygraph Association and certified by the American Assoc. of Police Polygraphists

Examiners

Jefferson's Polygraph

• Steps to becoming a licensed FP:– Prior to enrolling in the school, students must have a

baccalaureate degree or have five years of investigative experience and an associates degree.

– Students must attend and pass a 10-week intensive course. Curriculum includes psychology, physiology, ethics, history, question construction, psychological analysis of speech, chart analysis and test-data analysis.

– Students must enter an internship program and conduct a minimum of 25 exams for actual cases. These exams are faculty reviewed. This internship can take anywhere from eight months to one year.

• Following the completion of these requirements, the student becomes a polygrapher and may obtain a license in his or her state if that state requires one. There is no standardized test that all polygraph examiners must pass in order to practice.

Examiners

• Referred to as “Going to the box”• Pretest

– An interview between the examiner and examinee, where the two individuals get to learn about each other

– This may last about one hour – The examiner gets the examinee's side of the story concerning

the events under investigation– The examiner also profiles the examinee. The examiner wants to

see how the subject responds to questions and processes information.

• Design questions – The examiner designs questions that are specific to the issue

under investigation and reviews these questions with the subject.

Test Procedure

• In-test – The examiner asks 10 or 11 questions, only three of four of

which are relevant to the issue or crime being investigated. – Control questions: A very general question– If the person answers "no," the examiner can get an idea of the

reaction that the examinee demonstrates when being deceptive.

• Post-test – The examiner analyzes the data of physiological responses – Makes a determination regarding whether the person has been

deceptive. • If there are significant fluctuations that show up in the results,

this may signal that the subject has been deceptive, especially if the person displayed similar responses to a question that was asked repeatedly.

Test Procedure

Results

Source: Lafayette Instrument

Physiological responses recorded by a polygraph

• Misinterpretation of responses

• Inadmissibility in courts:– The human factor of a polygraph exam – The subjective nature of the test

• False positive - The response of a truthful person is determined to be deceptive

• False negative - The response of a deceptive person is determined to be truthful

• More false positives occur in real world biases against the truthful person– Examiner has not prepared the examinee properly – The examiner misreads the data following an exam

False Positives/False Negatives

• To cause a certain reaction that will skew the test's result – Subject attempts to have the same reaction to every

question so that the examiner cannot pick out the deceptive responses

– Can be found on internet or books

• Examples– Sedatives – Antiperspirant on fingertips – Biting tongue, lip or cheek – Controlled Breathing

Countermeasures

• Rarely admissible in court • New Mexico is the only state in the United States that

allows for open admissibility of polygraph exam results • In most cases, both sides of a legal case have to agree

prior to the trial that they will allow polygraphs to be admitted.

• On the federal level, the admissibility criteria are much vaguer and admission typically depends on the approval of the judge.

Legalities

• Private sector employees are protected by the Employee Polygraph Protection Act of 1988 (EPPA). – This law only affects commercial businesses– It does not apply to schools, prisons, other public

agencies or some businesses under contract with the federal government

• A business cannot require a pre-employment polygraph and cannot subject current employees to polygraph exams. A business is allowed to request an exam, but cannot force anyone to undergo a test. If an employee refuses a suggested exam, the business is not allowed discipline or discharge that employee based on his or her refusal.

E.P.P.A of 1988

• The electrodes can be alligator clips, electrode pads, or just wires and tape

• Attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions.

You know the subject is “lying” when the meter changes. • http://www.aaroncake.net/circuits/lie.htm

Homemade Polygraph

Video Clip

• American Polygraph Association • American Association of Police Polygraphists • AntiPolygraph.org • Federation of American Scientists: Polygraph Policy • Scientific Validity of Polygraph Testing • The Press Enterprise: Why people lie

Sources