Psychophysiological Detection of Deception

What is the basic assumption of lie detection?

Lying when faced with an apparently high probability of detection will induce anxiety that is measurable through physiological correlates

What are physiological correlates of lie induced anxiety?

Heart rate, respiratory rate, systolic blood pressure, galvanic skin response

What is the problem in lie detection?

Physiological changes are not unique to lying and not all liars show those changes

What were some low tech precursors to lie detectors?

Rice powder, bread and cheese: less salivation if anxious, can't chew

Boiling water/iron clearing: if wound was infected=guilty

What was Lombroso's (1800s) instrument designed to measure?

Blood volume changes

What was indicated by Lombroso's instrument if the air piston moved down?

Anxiety; reduced blood flow to hands=less air volume displaced

What is the Benussi ratio?

Ratio of many short inhalations and a long exhalation indicate anxiety

When was Benussi's work done?

Early 1900s

What did Marsten (1915) introduce to lie detection?

Systolic blood pressure deception test

What did Marsten's test form the basis of?

1923 Frye rule

What was the purpose of the Frye rule?

General acceptance test

-Would many peers be on board with the evidence in a criminal court?

What is Wonder Woman's magic truth lasso based on?

Marstens deception test

Who created the first modern polygraph?

Larson (1923)

What was Larson's polygraph?

Wrote changes in blood pressure in time with questions and responses

What is required to convert physiological measures to digital data in modern polygraphs?

Digital-analog converters

What are the uses of polygraphs?

-Verify claims (insurance)

-Assess potential/present employees (loyalty)

-Assess and monitor parolees (sex offenders)

-Force confessions

What is Marston's Relevant-Irrelevant Test (RIT)?

Two types of yes/no questions

-One relevant to the crime

-One irrelevant to the crime

What is the intention of the RIT?

Relevant questions should engender more anxiety and result in larger responses than irrelevant (to a guilty person)

How is deception determined with the RIT?

Ratio of R/I questions

What is the problem with the RIT?

Everybody will respond more the relevant questions (even if not guilty)

-How can a cutoff be determined?

What is the control question test (CQT)?

3 types of yes/no questions

-Irrelevant (ID, date of birth, etc)

-Relevant (incriminating)

-Control (provocative, but not incriminating)

What is required in creating control questions of the CQT?

Research into what is emotionally provocative for the person

What are control questions based on?

Verifiable info focusing on the subject's honesty

Where is the CQT used?

North America

What is the assumption of the CQT?

A guilty person will react more to R than C questions, but innocent people will react more to C than R questions

What is required at the beginning of administering the CQT?

An interview

What is a CQT interview intended to do?

-Convince subjects of high accuracy (can't beat it)

-Gather enough info to create meaningful C questions

How can subjects be convinced of high accuracy tests?

-Use fake or real stats

-Stacked card trick

What is the stacked card trick?

Give person a stack of cards (know the number and suit)

-Want them to lie

-Show that the lie can be detected (even though you know) even with low anxiety

How many questions are asked in the CQT?

30 sets each with control, relevant, and irrelevant questions

What score is given if the response to C>R?

+1 to +3

What score is given if C=R?

0

What score is given if C

-1 to -3

When would a +/- 3 be given instead of a 1?

If the response was much much greater

What isn't used in scoring CQT questions?

Irrelevant questions

How can CQT scores be interpreted?

-5 or less=fail

-4 to 4=inconclusive

over 5=pass

What is done if the subject fails a CQT?

Examiner confronts and attempts to elicit a confession

-Argue that it is easier to come clean

What are criticisms of CQT?

-Innocent subjects might react more strongly to R questions

-Guilty subjects might react more to C questions (attempting to conceal other crimes)

What can happen in attempting to elicit a confession?

An innocent person may confess

What is the guilty knowledge test (GKT)?

Determines if subject knows crime details that would only be available to the perpetrator

What might hinder effectiveness of GKT?

Media coverage

-Not often used in NA, mostly Israel

How is the GKT administered?

A statement is made with 5 multiple choice answers

-Only one is correct

What is the assumption of the GKT?

Guilty person (with knowledge of crime) will show most arousal to the correct answer

How should correct responses in the GKT be presented?

In pseudo random order

What are the odds of accidentally reacting to the correct answer in the GKT?

1/5

What are the odds of accidentally reacting to the correct answer in the GKT 10 times in a row?

1/10,000,000

How can validity of lie detector tests be tested?

Mock crimes and field trials

What is the design of mock crimes?

Subjects are asked to act out certain crimes

-Later undergo polygraphed-blinded exam, instructed to lie

What is the disadvantage of mock crimes?

Emotional reactions are likely much smaller, so sensitivity may be underestimated

What is the advantage of mock crimes?

Ground truth is known by experimenter (if they did it or not)

What can increase emotional reactions of participants in mock crime experiments?

Offer them money (put skin in the game)

What is the design of field trials?

Accuracy rates are assessed post-conviction using real criminals

What is the advantage of field trials?

Less artificial (likely more legitimate scores)

What is the disadvantage of field trials?

Ground truth is based on confession or results of court proceedings (witness reports)

-Both can be distorted

What was found in comparing blind vs non blind CQT raters?

Blind raters scored worse

-Especially in innocent condition (many false positives)

What is suggested by CQT data comparing blind and non blind raters?

Ambiguous situations are dangerous

-Can result in incorrect determination of guilt/innocence

What was the hit rate for original examiners?

90%

What was the hit rate for blind raters?

55%

What is found, given CQT data, regarding responses by innocent people?

They DO respond more to relevant than control questions

Why were the original examiners more accurate than blind raters?

Based their opinions on factors beyond physiological measures

How did Honts, Raskin & Kircher (1994) argue a polygraph test could be undermined?

-Count backwards by 7 (occupy mind, focus less on questions)

-Press toes against ground

-Bite tongue in response to controls

How can a polygraphed catch cheating?

Counter measures, such as pressure mats under the feet

How much better are psychopaths at faking polygraphs?

Not at all

Why are polygraphs not accepted in Canada?

R v Beland:

-Mystique of science, level of authority over judge is objectionable

Why are polygraphs a constitutional issue?

You can't be compelled to give evidence against you

Who dissented against the R v Beland ruling?

2 SCJ's

When will certain states accept polygraphs?

If there is agreement by prosecutor and defense prior to test

What criteria are not met by polygraphs?

Frye or Daubert

What is Daubert (1993) criteria?

-Empirical testing (falsifiable?)

-Subjected to peer review

-Known or potential error rate

-Existence and maintenance of operation standards

-Degree of acceptance by scientific community

What were Daubert criteria made after?

Thalidomide class action suit

What is the error distribution of polygraph tests?

False positives are much greater than false negatives

How are polygraphs standardized?

Not, many different instruments and people used of different quality and training

What are evidentiary standards of polygraphs?

-Frye test

-Daubert criteria

-Mohan

-Inherent problems

What did Dr Yarmy give as reference to Mohan?

-Irrelevant info

-Not assisting with the suit

-Not a qualified expert in field (pedophilia)

What are the inherent problems of polygraphs?

-Experts may inadvertently become decision makers

-Research findings can't be cross examined

-Costly, time consuming

-Lack of expert consensus (technical and ethical)

-Called "junk science"

Why shouldn't you do a forensic assessment with someone who was your patient?

Greater investment in patient's wellbeing (helps them)

-May gain information throughout treatment that patient normally wouldn't provide given crime committed (doesn't help them)

What is a polygraph just as accurate as in measuring physiological response to standard questions?

fMRI

Do experts concern themselves with the quality of polygraphs?

No, rather the ethics/technicalities