Encyclopedia of Psychology and Law

The third weakness of the CKT concerns counter-

measures—that is, things that a deceptive person

might do in an effort to defeat or distort the test.

Research shows the CKT to be susceptible to mental

and physical countermeasures if subjects are knowl-

edgeable about the technique and have received train-

ing in the use of countermeasures.

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Although a great deal is written about the CKT in

the scientific literature, it presently has very little

application in either law enforcement or national

security. There is essentially no application of the

CKT in the United States. The only country that

reports a general use of the CKT in law enforcement

is Japan. In Japan, persons with special training in

psychology and eyewitness memory are part of the

crime scene investigation team, and they actively

search for and document possible bits of information

for use in CKT when the crime scene is first investi-

gated. It may be that this careful crime scene docu-

mentation results in a higher rate of applicability for

the technique. However, a clear explanation of how

Japanese examiners overcome the memorability prob-

lem is not presently in evidence.

The Deception Approach

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The Relevant-Irrelevant Test. The deception approach

asks direct accusatory questions (referred to as

Relevant questions) under the assumption that persons

attempting deception will produce physiological

responses when they lie. The earliest version of the

deception approach was the Relevant-Irrelevant Test

(RIT). Along with direct accusatory questions (e.g.,

Did you shoot John Doe?), the RIT also asks irrele-

vant (neutral) questions, to which the person is

assumed to be responding truthfully (e.g., Are the

lights on in this room?). The working assumption of

the RIT is that persons attempting deception will pro-

duce a large and consistent physiological response to

the relevant questions, whereas the truthful will not

distinguish between the irrelevant and the relevant

questions.

Virtually all the scientists who work in this area

dismiss the working assumptions of the RIT as naive.

Clearly the truthful will recognize the relevant ques-

tions as the more important class of stimuli and are

thus likely to produce physiological responses to

them, and in fact, research does show a very large

number of false-positive outcomes to the RIT. As a

result, the RIT has very little application in forensic

polygraph testing. However, the RIT is still in use for

periodic screening of sex offenders and in screening

job applicants. At this time, any use of the RIT is

highly controversial, and the scientists active in this

area do not support its use.

Comparison Question Tests.John Reid developed the

notion of an active comparison question in the context

of law enforcement examinations during the late 1940s

in response to the obvious problems with the RIT. The

idea of the active comparison question was to provide

a stimulus in the test that would evoke physiological

responses from the innocent but not from the guilty.

The comparison question took the form of a question

that the subject was probably going to respond to with

a lie. For example, after discussing the death of John

Doe and after the subject of the examination has

denied being involved in John Doe’s death, the poly-

graph examiner would tell the subject that he or she is

going to be asked some questions about his or her

basic character in an effort to show that he or she is not

the type of person who would have shot John Doe. The

subject would then be asked a question such as

“Before the year 2006, did you ever hurt someone?”

The comparison question is deliberately vague and

covers a long period of time. In the context of the

examination, the subject is led to believe that an affir-

mative response is damaging because it shows that he

or she is the kind of person who would have commit-

ted the crime. However, for virtually all subjects, it can

be assumed that a definitive “No” response is probably

a lie in view of the deliberately vague presentation of

the comparison question.

The working assumption of the Comparison

Question Test (CQT) is that guilty participants will

produce consistent physiological responses to the

relevant questions, while they will respond only

minimally to the comparison questions. Although the

guilty are assumed to be lying in their answers to the

comparison questions, it is assumed that the compar-

isons are likely to be viewed as unimportant compared

with the relevant questions, which directly address the

issues under investigation. The innocent are expected

to respond more to the comparison questions because

they know that they are lying or are at least uncertain

about the veracity of their answers to the comparison

questions, whereas they know they are responding

598 ———Polygraph and Polygraph Techniques

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