Polygraphy
The Science of Lie Detection
Operational Terms


POLYGRAPH – is an instrument for the
recording of changes in blood pressure; pulse
rate, respiration and skin resistance as
indication of emotional disturbances especially
of lying when questioned.
The word was derived from the word POLY
means “many” and GRAPHS means “writing
chart”.



POLYGRAPHY – it is the scientific method of
detecting deception, using a polygraph
machine.
FEAR – is emotional response to specific
danger that appears to beyond a persons
defensive power.
STIMULUS – is a force or motion reaching
the organism and excites the receptors.


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REACTION – it is an action in mental attitude
evokes by external influence.
DECEPTION – is an act of deceiving or
misleading usually accompanied by lying.
DETECTION – It is an act of discovery of
existence, presence of fact or something
hidden or obscure.
LYING – the uttering or conveying of
falsehood or creating a false or misleading
information with the intention of affecting
wrongfully the acts and opinion of other.


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RESPONSE – is any activity or inhibition of
the previous activity of an organism resulting
from stimulation.
SPECIFIC RESPONSE – is any deviation
from the normal tracing of the subject.
NORMAL TRACING – is a tracing on the
chart wherein the subject answered in the
irrelevant question.
POLYGRAPH EXAMINER – is one who
conducts and administer the test.


CHART OR POLYGRAMS – refers to the
composite
records
of
pneumograph,
Galvanograph
and
cardiosphygmograph
tracings recorded from series of questions.
Subject – refers to the person being examined.
Early Methods of detecting
deception

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Trial by Combat
Trial by Ordeal
Trial by Iron Hot Ordeal
Ordeal by Balance
Ordeal of Rice Chewing
Donkey’s Tall Ordeal
Polygraph

The polygraph is used to test or question
individuals for the purpose of detecting
deception or verifying truth of statements
through a visual, permanent and
simultaneous recording of a person’s
cardiovascular and respiratory pattern as
a minimum instrumentation requirement.

A polygraph (commonly referred to as a lie
detector) is an instrument that measures and records
several physiological responses such as:




blood pressure,
pulse,
respiration and
skin conductivity
while the subject is asked and answers a series of questions,
on the basis that false answers will produce distinctive
measurements. The polygraph measures physiological
changes caused by the sympathetic nervous system during
questioning.
Within the U.S. federal government,
a polygraph examination is also
referred to as a
PSYCHOPHYSIOLOGICAL
DETECTION OF DECEPTION
(PDD) examination. Several other
technologies are also used in the
field of lie detection, but the
polygraph is the most famous.
History

The idea that lying produces physical side-effects has
long been claimed. In West Africa persons suspected
of a crime were made to pass a bird's egg to one
another. If a person broke the egg, then he or she was
considered guilty, based on the idea that their
nervousness was to blame. In ancient China the
suspect held a handful of rice in his or her mouth
during a prosecutor's speech. Since salivation was
believed to cease at times of emotional anxiety, the
person was considered guilty if by the end of that
speech the rice was dry.
1895

Cesare Lombroso, an Italian scientist,
employed the first scientific instrument to
detect
deception
–
HYDROSPHYMOGRAPH,
measured
changes in pulse and blood pressure when
suspects were questioned about their
involvement of a specific offense.
1914

VITTORIO
BENUSSI
successfully
detected
deception
with
a
PNEUMOGRAPH – an instrument that
graphically measures an examinee’s
inhalation and exhalation. Benussi thus
demonstrated that changes in breathing
patterns accompany deception.
1917

Further research by WILLIAM
MARSTON in 1917 dealt with
the SPHYGMOMANOMETER,
which was used to obtain periodic
discontinuous blood pressure
readings during the course of an
examination.
1920

A device recording both blood-pressure and
galvanic skin response was invented in
1920 by Dr. John A. Larson of the
University of California and first applied in
law enforcement work by the Berkeley Police
Department under its nationally renowned
police chief August Vollmer

Further work on this device was
done by Leonarde Keeler.[2] The
first time the term "polygraph"
was used was in 1906 by James
MacKenzie in his invention the
"ink polygraph," which was used
for medical reasons.
.

Makenzie wrote a second paper on the concept in 1915, when
finishing his undergraduate studies. He entered Harvard Law
School and graduated in 1918, re-publishing his earlier work
in 1917.[3] According to their son, Marston's wife, Elizabeth
Holloway Marston, was also involved in the development of
the systolic blood-pressure test: "According to Marston’s son,
it was his mother Elizabeth, Marston’s wife, who suggested to
him that 'When she got mad or excited, her blood pressure
seemed to climb' (Lamb, 2001). Although Elizabeth is not
listed as Marston’s collaborator in his early work, Lamb,
Matte (1996), and others refer directly and indirectly to
Elizabeth’s work on her husband’s deception research. She
also appears in a picture taken in his polygraph laboratory in
the 1920s (reproduced in Marston, 1938)."[4][5] The comic
book character, Wonder Woman by William Marston (and
influenced by Elizabeth Marston[6][7] ) carries a magic lasso
which was modelled upon the systolic blood-pressure
test.[8][6]

Marston was the self proclaimed “father of the
polygraph”
despite
his
predecessor's
contributions. Marston remained the device's
primary advocate, lobbying for its use in the
courts. In 1938 he published a book, The Lie
Detector Test, wherein he documented the
theory and use of the device.[9] In 1938 he
appeared in advertising by the Gillette
company claiming that the polygraph showed
Gillette razors were better than the
competition.[10][11][12]
CARDIOSPHYGMOGRAPH

CESARE LOMBROSO – accorded
as the first person that utilizes
instrument in detecting deception.
His basis in detecting deception is by
measuring the blood pressure and pulse
rate.
 This
is
known
as
HYDROSPHYGMOGRAPH

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ANGELO MOSSO – he stated that
FEAR influenced the heart and could
be use as a basis for detecting
deception. He uses sphygmanometer
and scientific radio to study fear

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DR. WILLIAM MARSTON
–
he conducted numerous tests for
detecting deception and utilizes the
change in systolic pressure to determine
deception.
He also developed his own method of
reading systolic blood pressure.
Self proclaim father of polygraph


JOHN A. LARSON
– the real
“Father of lie detection”.
The present polygraph machine is
attributed to him. He is the en who
develop and study to record at the same
time the responses of the blood pressure,
pulse rate and respiration
GALVANOGRAPH COMPONENT

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STICKER – he introduced the method of
detecting deception from the galvanic
impression on the chart tracing.
VERGUTH
–
he
used
the
word
PSYCHOGALVANIC reflex. He believed that
electrical phenomena are due to the activity of
sweat glands, and such activity is known as
“psychogalvanic”.
PNEUMOGRAPH COMPONENT

VITTORIO BENUSSI – he noted changes in
inhalation ratio during indications of
deceptions.
LEONARD KEELER


he device a metal recording bellows; rolled
chart paper.
In 1949, he incorporated Galvanograph with
measurement of blood pressure and respiration
into a portable case.
The four Major components
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PNEUMOGRAPH
CARDIOSPHYGMOGRAPH
COMPONENT
GALVANOGRAPH COMPONENT
KEYMOGRAPH COMPONENT

Today, polygraph examiners use two
types of instrumentation:
analog
 computerized

In the United States, most examiners now
use computerized instrumentation.
An analog polygraph instrument
Most analog polygraphs are being replaced by digital
devices.
Today, most polygraph exams are administered with digital equipment
like this.

The polygraph instrument has undergone a
dramatic change in the last decade. For many
years, polygraphs were those instruments that
you see in the movies with little needles
scribbling lines on a single strip of scrolling
paper. These are called analog polygraphs.
Today, most polygraph tests are administered
with digital equipment. The scrolling paper has
been replaced with sophisticated algorithms
and computer monitors.

Modern scientific methods have been devised
utilizing
knowledge
of
physiology,
psychology, pharmacology, toxicology, etc. in
determining whether a subject is telling the
truth or not. Although a scientific method of
deception detection have not yet attain legal
recognition to have their results admissible as
an evidence in court, they have been
considered very useful as aids in criminal
investigation.
Methods of deception detection
1.
2.
3.
4.
5.
6.
Devices which record the psychophysiological response.
Use of drugs that try to inhibit the inhibitor
Hypnotism
By observation
Scientific Interrogation
Confession
Recording the Psycho physiological
Response:

The nervous control of the human body
includes the central nervous system (the
brain and the spinal cord) and the
autonomic or regulating nervous system
(sympathetic and parasympathetic). The
central nervous system primarily controls
the motor and sensory functions that
occur at or above the threshold. It maybe
voluntary.

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
The autonomic nervous system acts as a
self-regulating autonomic response of the
body.
The autonomic nervous system is
composed of two complimentary
branches: the sympathetic and the
parasympathetic nervous system, acting
opposite each other.
The fibers of both enervate all organs
where self-regulation is essential

When a person is under the influence of
physical (exertion) or emotional (anger,
excitement, fear, lie detection, etc.)
stimuli, the sympathetic will dominate
and over-ride the parasympathetic, thus
there will be a changes in the heart rate,
pulse rate, blood pressure, respiratory
tracing, psycho galvanic reflexes, time of
response to question, voice tracing, etc.

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The parasympathetic nervous system works to
restore things to normal when the conditions of
stress have been removed. It is the dominant
branch when the condition is normal and the
subject is calm, contented and relaxed.
The recording of some of the psychophysiological reaction of a subject when he is
subjected to a series of questions, and the
scientific interpretation by trained experts are
the basis of the tests.
Word Association Test
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A list of stimulus and non-stimulus words are
read to the subject who is instructed to answer
as quickly as possible.
The answer to the questions may be a “yes” or
a “no”.
Unlike the lie detector , the time interval
between the words uttered by the examiner and
the answer of the subject is recorded.

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When the subject is asked questions with
reference to his name, address, civil status,
nationality, ect. Which has no relation to the
subject-matter of the investigation, the
tendency is to answer quickly.
But when the questions bear some words
which have to do with the criminal acts the
subject allegedly committed, like knife, gun, or
hammer which was used in the killing, the
tendency is to delay the answer.
The test is not concerned with the
answer, be it a ‘yes” or a “no”. The
important factor is the time of
response in relation to stimulus or
non-stimulus words.
 Like the use of the lie detector, the
subject cannot be compelled to be
subjected to the test without his
consent.

Psychological Stress Evaluator

When a person speaks, there are audible
voice frequencies and superimposed on
these are the inaudible frequency
modulations which are products of
minute oscillation of the muscles of the
voice mechanism. Such oscillations of the
muscles micro tremor occur at the rate of
8 to 14 cycles per second and controlled
by the central nervous system.
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When the person is under stress as when
he is lying, the micro tremor in the voice
utterance in moderately or completely
suppressed.
The degree of suppression caries
inversely to the degree of psychologic
stress in the speaker.
The psychological stress evaluator (PSE)
detects, measures, and graphically
displays the voice modulations that we

When a person is relaxed and responding
honestly to the questions, those inaudible
frequencies are registered clearly on th
instrument. But when a person is under
stress, as when he is lying, these
frequencies tend to disappear.
Procedure:


The examiner meets the requesting party to
determine the specific purpose of the
examination and to begin formulation of
relevant questions.
A pre-test interview is conducted with the
subject to help him or her feel at ease with the
examiner, to provide an opportunity to specify
matters, to eliminate outside issues, and to
review questions that will be asked.
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An roal test of about 12 to 15 “yes” or “no”
questions or given which is recorded on a tape
recorder. The questions are a mixture of
relevant and irrelevant questions.
Immediately following the test or at a later
time, the tape is processed through the
Psychological Stress Evaluator for analysis of
the answers.
If stress is indicated, the subject is given
opportunity to provide additional clarification.
A retest is given to verify correction and
clarification.
Use of Drugs that “Inhibit the
Inhibitor”
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Administration of the TRUTH SERUM
Narcoanalysis/Narcosysthesis
Intoxication with Alcohol
TRUTH SERUM
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The term “ truth serum” is a misnomer. The
procedure does not make someone tell the
truth and the thing administered is not serum
but actually a drug.
In the test, HYOSCINE HYDROBROMIDE is
given hypodermically in repeated doses until a
state of delirium is induced.
When the proper point is reached, the
questioning begins and the subject fells a
compulsion to answer the questions truthfully.


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He forgets his alibi which he may have built
up to cover his guilt. He may give details of
his acts or may even implicate others.
The drug acts as depressant in the nervous
system. Clinical evidence indicates the various
segments of the brain particularly the cortex.
Statements taken from the subjects while under
the influence of truth serum are evolutionary
obtained hence they are not admissible as
evidence.
Narcoanalysis/Narcosynthesis
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This method of deception detection is
practically the same as that of administration
of truth serum. The only difference is the drug
used. Psychiatric sodium amytal or sodium
penthotal is administered by the subject.
When the effects appear , questioning starts.
It is claimed that the drug causes depression of
the inhibitory mechanism of the brain and the
subjects talk freely.


The administration of the drug and
subsequent interrogation must be done by
a psychiatrist with along experience on
the line.
Like the administration of the truth
serum, the result of the test is not
admissible.
INTOXICATION

The apparent stimulation effect of alcohol
is really the result of the control
mechanism of the brain. The apparent
stimulation effect of alcohol is really the
result of the control mechanism of the
brain, so alcohol, like truth serum and
narcoanalysis
drugs
“inhibit
the
inhibitor”.

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The ability of alcohol to reveal the real
person behind the mask which all of us
are said to wear (“mask of sanity’) is
reflected in the age-old maxim, IN VINO
VERITAS (“in wine there is truth”).
The person whose statement is to be
taken is allowed to take alcoholic
beverages to almost intoxication.


Confessions made by the subjects while
under the influence of alcohol may be
admissible if he is physically capable to
recollect the facts that he has uttered after
the effects of alcohol have disappeared.
But in most intances, the subjects cannot
recall everything that he had mentioned
or he may refuse to admit the truth of the
statement given.

The knowledge of the truth is an
essential requirement
for
the
administration of criminal justice.
The success or failure in making
decisions may rest solely on the
ability to evaluate the truth or falsity
of the statement given by the
suspects or witness. The task for its
determination initially lies on the
hand of the investigator.
HYPNOSIS


It is the alteration of consciousness and
concentration in which the subject
manifests a heightened of suggestibility
while awareness is maintained.
Not all persons are susceptible to
hypnotic induction. Subjects who are
compulsive-depressive type, strongwilled
like
lawyers,
accountants,
physicians and other professionals are
usually non-hypnotizable.
REASONS: (why it is not admissible
in court)


It lacks the general scientific acceptance
of the reliability of hypnosis per se in
ascertaining the truth from falsity.
The fear that the Trier of fact will give
uncritical and absolute reliability to a
scientific device without consideration of
its flaw in ascertaining veracity.

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The possibility that the hypnotized subject will
deliberately fabricate.
The prospect that the state of heightened
suggestibility in which the hypnotized subject
is suspected will produce distortion of the fact
rather than the truth.
The state of the mind, skill and
professionalism of the examiner are too
subjective to permit admissibility of the expert
testimony.
Physiological
&
Psychological Symptoms
of
GUILT
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

SWEATING- sweating accompanied with a flushed
face indicate anger, embarrassment or extreme
nervousness. Sweating with a palled face may indicate
shock of fear. Sweating hands indicate tension.
COLOR CHANGE – if the face is flushed, it may
indicate anger, embarrassment or shame. A pale face
is a more common sign of guilt.
DRYNESS OF THE MOUTH – nervous tension
causes reflex inhibition of salivary secretion and
consequently dryness of the mouth. This causes
continuous swallowing and licking of the lips.


Excessive activity of the Adam’s apple - on
account of the dryness of the throat aside from
the mouth, the subject will swallow saliva
from the mouth and this causes the frequent
upward and downward movement of the
Adam’s apple.
Fidgeting – subject is constantly moving about
in the chair, pulling his ears, rubbing his face,
picking and tweaking the nose, crossing or
uncrossing the legs, rubbing the hair, eyes,
eyebrows, biting or snapping of fingernails.
These are indicators of nervous tension.


Peculiar Feeling Inside – there is a sensation
of lightness of the head and the subject is
confused. This is the result of his troubled
conscience.
Swearing to the truthfulness of his assertion –
usually a guilty subject frequently utters such
expression. “I swear to God I am telling the
truth” or “ I hope my mother drops dead if I
am lying”, “I swear to Go”…etc. Such
expressions are make to make forceful and
convincing his assertion of innocence.


Spotless past record - “Religious man” – the
subject may assert that it is not possible for
him to do “anything like that” inasmuch as he
is a religious man and that he has a spotless
record.
Inability to look at the investigator “straight in
the eye” – the subject does not like to look at
the investigator for fear that his guilt may seen
in his eyes. He will rather look at the floor or
ceiling.

“Not that I remember” expression –
the subject will resort to the use of
“Not that I Remember” expression
when answering to be evasive or to
avoid
committing
something
prejudicial to him.
LIE


Is also called PREVARICATION
A type of deception in the form of an
untruthful statement with the intention to
deceive, often with further intention to
maintain a secret of reputation, to protect
someone’s feelings from getting hurt, or to
avoid punishment.
Classification of Lies
Bald-Faced lie


A bald-faced ( or barefaced) lie is a lie
that is told when it is obvious to all
concerned that is it a lie.
Example: a child who has chocolate all
over his face and denies that he has eaten
the last piece of chocolate cake, is a baldface liar.
Lying by omission

One lies by omission by omitting an
important fact, deliberately leaving
another person with a misconception.
Lying by omission includes failures
to
correct
pre-existing
misconceptions.
Lie-to-children

A lie-to-children is a lie, often a
platitude that may use euphemism,
that is told to make an adult subject
acceptable to children. A common
example is “ The stork brought you”.
White lie



A white lie would cause no discord if it were
uncovered and offers some benefit to the liar,
the hearer, or both.
White lies are often used to avoid offense,
such as telling someone that you think that
their new outfit looks good when you actually
think that it is a horrible excuse for an outfit.
The lie is told to avoid the harmful
implications and realistic implications of the
truth.
NOBLE LIE



A noble lie is one that would normally cause
discord it if were uncovered, but that offers
some benefit to the liar and perhaps assist in an
orderly society and thus potentially gives some
benefit to others also.
It is often told to maintain law, order and
safety.
A noble lie usually has the effect of helping an
elite maintain power.
EMERGENCY LIE


An emergency lie is a strategic lie told when
the truth may not be told because, for example,
harm to a third party would come of it.
Example: a neighbor might lie to an engaged
husband about the whereabouts of his
unfaithful wife, because said husband might
reasonably be expected to inflict physical
injury to his husband.
PERJURY


It is the act of lying or making verifiably false
statements on an material matter under oath or
affirmation in a court of law or in any of
various sworn statements in writing.
Perjury is a crime because the witness has
sworn to tell the truth and, for the credibility of
the court, witness testimony must be relied on
an being truthful.
BLUFFING

Pretending to have capability or intention one
doesn’t. Bluffing is an act of deception that is
not usually seen as immoral because it takes
place in the context of a game where this kind
of deception is consented to in advance by the
players.
MISLEADING

A misleading statement is one where there
isn’t an outright lie, but still has the purpose of
making someone believe in an untruth.
DISSEMBLING


A polite term for lying, though some might
consider it to refer to being merely misleading.
It is merely considered to be a euphemism for
lying.
EXAGGERATION

An exaggeration occurs when the most
fundamental aspect of a statement is true, but
the degree to which it is true is not correct.
JOCOSE LIE



Are lies that are meant in jest and are usually
understood as such by all present parties.
Sarcasm can be an example.
Storytelling traditions that are present in some
places, where the humor comes form the
storyteller’s insistence that he or she is telling
that absolute truth despite all evidence to the
contrary.
PROMOTION LIES

Advertisements often contain statements that
are not credible, such as “we are always happy
to give a refund.”
BELIEF SYSTEMS


It is alleged that some belief systems may find
lying to be justified.
Example: Religious lies
Augustine’s Taxonomy of Lies
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Lies in religious teaching.
Lies that harm others and help no one.
Lies that harm others and help someone.
Lies told for the pleasure of lying
Lies told “please others in smooth discourse”.
Lies that harm no one and that help someone.
Lies that harm no one and that save someone’s life.
Lies that harm no one and that save someone’s purity.
Lying in the bible


The Hebrew midwives lied to the king of
Egypt rather than carry out his order to kill all
male Hebrew babies; the midwives did this
because they “feared God” . (Exodus 1:15-20)
Rehab lied to the king of Jericho about hiding
the Hebrew spies (Joshua 2:4-5) and was not
killed with those were disobedient because of
her faith (Hebrews 11:13)


Delilah repeatedly accused Samson of lying to
her (Jg. 16:10-13) as she interrogated him
about the source of his strength.
Abaraham instructs his wife, Sarai, to lie to the
Egyptians and say that she is his sister (Gen
12:10), which leads to the Lord punishing the
Egyptians (Gen 12:17-19).
Consequences of Lying


Discovered – discovery of lie tends to discredit
other statements by the same speaker and can
lead to social and legal sanctions againsts the
speaker.
Remain Undiscovered – undiscovered lie is a
latent danger to the liar who us probably aware
that it may be discovered.
Representations of Lying


Carlo Collodi’s PINOCCHIO is a wooden
puppet often led into trouble by his propensity
to lie. His nose grows with every lie. A long
nose has thus become a caricature of liars.
In the film LIAR LIAR, the lawyer Fletcher
Reed (Jim Carrey) cannot lie for 24 hours due
to a wish of his son which magically came
true.


In 1985 MAX HEADROOM, the title
character comments that one can always tell
when a politician lies because ‘their lips
move”. The joke has been widely repeated and
rephrased.
In the film BIG FAT LIAR, the story which
producer Marty Wolf, a notorious and proud
liar himself. Each lie he tells causes him to
grow in size.
POLYGRAPHY
The science of Lie Detection
The Polygraph Instrument

The polygraph instrument usually measures
four to six physiological reactions recorded by
three different medical instruments that are
combined in one machine. Older polygraph
machines were equipped with long strips of
paper that moved slowly beneath pens that
recorded the various physiological responses.
Newer equipment uses transducers to convert
the information to digital signals that can be
stored on computers and analyzed using
sophisticated mathematical algorithms.
CARDIO-SPHYGMOGRAPH

Blood pressure and heart rate are
measured by the cardio-sphygmograph
component of the polygraph, which
consists of a blood pressure cuff that is
wrapped around the subject's arm.

During the questioning the cuff remains
inflated.

The movement of blood through the
subject's veins generates a sound that
is transmitted through the air in the
cuff to a bellows that amplifies the
sound. The magnitude of the sound
relates to the blood pressure and the
frequency of the changes in the
sound relates to the heart rate.
PNEUMOGRAPH COMPONENT

The pneumograph component of the
polygraph
records
the
subject's
respiratory rate. One tube is placed
around the subject's chest and a second is
placed around his or her abdomen. These
tubes are filled with air. When the subject
breaths, changes in the air pressure in the
tubes are recorded on the polygraph.
GALVANOGRAPH


The galvanograph section records the
amount of perspiration produced.
It consists of electrical sensors called
galvanometers that are attached to the
subject's fingertips. The skin of the
fingertips contains a high density of
sweat glands, making them a good
location to measure perspiration.


As the amount of sweat touching the
galvanometers increases, the resistance of
the electrical current measured decreases
and these changes are recorded by the
polygraph.
Most forensic psychophysiologists (FPs)
consider the cardiosphygomgraph and the
pneumograph
components
more
informative than the galvanograph.
KEYMOGRAPH

Keymograph component is a motor
that pulls or drives the chart paper
under
the
recording
pen
simultaneously at the rate of 6 or 12
inches per minute.
The Examination Room







It must be private and free from all outside noise and
detracting influences.
Adequately lighted and well ventilated
Devoid of pictures, paintings, decors or other
ornaments.
Preferably sound-proof
Without any furniture other than a polygraph desk.
Subjects chair with arm rest and an examiner’s stool.
With one-way mirror and remote sound system for
monitoring the test proceedings to an authorized
audience.
The polygraph examiner


TECHNICALLY, he must have a
complete knowledge of the instrument
and its capabilities and limitations.
MORALLY – maintain a high personal
integrity
and
increasing
personal
proficiency through constant study and
research.



He constantly bears in mind his primary
obligation to his subjects is to afford
them all possible safeguards against error
and must not accept any subjects whose
physical or mental health or state makes
him unfit.
He is an impartial seeker of truth.
Never allow his personal feelings,
sympathies, or prejudice influence the
results of the examination.
Selection of Test Subject


Permanent physical illness such as mental
derangement, certain heart condition, breathing
disorder, and addiction to narcotic drugs are definite
causes that makes a person unfit for a polygraph test.
Temporary illness and conditions such as sickness,
injury, pain, physical discomfort, external physical or
mental fatigue, colds, coughs, fever, allergies, and
influences of sedatives and liquor are causes for
deferment of the test until such time that the subjects
regains his ordinary physical condition.



Treatment of the subjects before being asked
to make or while awaiting test affects the
success of the examination.
Prolonged
interrogation
with
constant
accusation directed against the subjects may
condition him to react falsely to the test, or
may result to a flat emotionless chart.
A person’s daily habit should not be upset
more than necessary. Long delay should be
avoided.
PHASES of EXAMINATION
PRE-TEST INTERVIEW
 ACTUAL
interrogation and
recording
through
the
instrument
 POST-TEST INTERVIEW

Initial Interview with the
Investigator

Test question are formulated by the
polygraph
examiner
based
from
information
obtained
from
the
investigator. General facts, theories and
suspicions are not enough basis for a
polygraph test. Question formulation
depends greatly upon detailed and
accurate information regarding all the
available facts.
The investigator on case should personally inform the
examiner of such facts as:

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

Unpublicized facts of the offense known only
to the victim, the investigator and the offender.
Specific articles or exact amounts of money
stolen.
Exact time and place the offense occurred.
Peculiar aspects of the offense or any strange
or obscene acts committed at the scene.

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Known facts about a suspects action or
movements immediately preceding of after the
incidents.
Facts indicating a connection between
suspects, victims and witnesses, especially
when they deny any connection.
Exact type of firearm, weapon or tool used.
Results of laboratory test if any.
Background information particularly previous
police records or verifies facts which subjects
denies.
PRE-TEST INTERVIEW

Before the actual testing is done, the examiner
must first make an informal interview of the
subject which may last from 20 to 30 minutes.



To condition the subject psychologically for
the test.
The subject is appraised of his constitutional
rights.
A written consent which must be freely and
voluntary given is taken.
Purpose of the Pre-Test Interview



To determine whether the subject has any
medical or psychiatric condition or has used
drugs that will prevent the testing.
To explain to the subject the purpose of the
examination.
To develop the test questions, particularly
those of the types to be asked.
To relieve the truthful subject of any
apprehension as well as to satisfy the
deceptive subject as to the efficiency
of the technique.
 To know any anti-social activity or
criminal record of the subject.

Question Formulation


Questions formulated are short, simple
and direct answerable by either ‘Yes” or
“No” only, phrased in the language easily
understood by the subjects.
The questions must be clear and must
have reference to only one element of an
offense of fact.
Types of question
IRRELEVANT
RELEVANT
CONTROL

IRRELEVANT QUESTIONS



These are questions which have no bearing to
the case under investigation.
The question may refer to the subject’s age,
educational attainment, marital
status,
citizenship, occupation, etc.
The examiner asks these types of questions to
ascertain the subject’s normal pattern of
response by eliminating the feeling of
apprehension.
RELEVANT QUESTIONS



These are questions pertaining to the
issue under investigation. They must be
unambiguous,
unequivocal
and
understandable to the subject.
They must be related to one issue or one
criminal act.
It is equally important to limit the number
of relevant questions to avoid discomfort
to the subject.
Control Questions

These are questions which are
unrelated to the matter under
investigation but are of similar nature
although less serious as compared to
those relevant questions under
investigation.
Test Construction applied are of two
main types.
General Peak Tension Test
 Peak of Tension Test

General Peak Tension Test


1.
2.
The general question test consist of a
series of relevant and irrelevant
questioned asked in a planned order.
Example:
Have you ever been called by the name
Fred? (Irrelevant)
Is today Friday? (Irrelevant)

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
Do you have anything to do with the robbery
at Goodwill Grocery last night? (relevant)
Did you robbed the Goodwill Grocery last
night? (relevant)
Are you over twenty years of age? (irrelevant)
Do you know is any of the fingerprints found
at goodwill Grocery is yours? (relevant)
Do you drink water? (Irrelevant)
Do you know of anyone involved in the
robbery of Goodwill Grocery last night?
(Relevant)
Peak of Tension Test


1.
2.
3.
4.
This valid test is only made when there is no
widespread publicity about the crime.
Example:
Do you know whether the stolen watch from
Fred is Boluva?
It is an Elgin?
Is it a Colorado?
Is it a Rolex?
POST-TEST INTERROGATION



To clarify the findings
To learn if there are any other reasons for the
subject’s responding to a relevant question,
other than the knowledge of the crime.
To obtain additional information and an
admission for law enforcement purposes, if he
results suggest deception.
There are three basic approaches to
the polygraph test:
The Control Question Test (CQT).
 The Directed Lie Test (DLT).
 The Guilty Knowledge Test (GKT).

The Control Question Test (CQT)

This test compares the physiological
response to relevant questions about the
crime with the response to questions
relating to possible prior misdeeds. "This
test is often used to determine whether
certain criminal suspects should be
prosecuted or classified as uninvolved in
the crime" (American Psychological
Association).
The Directed Lie Test (DLT)

This test tries to detect lying by
comparing physiological responses
when the subject is told to
deliberately lie to responses when
they tell the truth.
The Guilty Knowledge Test (GKT)

This test compares physiological
responses to multiple-choice type
questions about the crime, one choice
of which contains information only
the crime investigators and the
criminal would know about.
Objectives




Ascertain if a person is telling the truth
by verifying statement and/or comparing
conflicting statements.
Obtain additional investigative leads to
the facts of an offense.
Locate fruits or roots of crime or
whereabouts of wanted persons.
Identify other persons involved.
Obtain valuable information from
reluctant witnesses.
 Most important is the elimination of
innocent suspects.

Limitations




It is an invaluable investigation aid, but never
a substitute for investigation.
It is a lie detector, it is not a scientific
diagnostic instrument.
It does not determine facts, it records
responses to that which the subject knows to
be true.
It is only as accurate as the examiner is
competent.

The underlying theory of the polygraph is that
when people lie they also get measurably
nervous about lying. The heartbeat increases,
blood pressure goes up, breathing rhythms
change, perspiration increases, etc. A baseline
for these physiological characteristics is
established by asking the subject questions
whose answers the investigator knows.
Deviation from the baseline for truthfulness is
taken as sign of lying
Test Procedure
Not more than 12 questions
 At least three (3) charts are taken,
each lasting not more than four (4)
minutes,
 5 to ten minutes between charts.

Chart Marking


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
Beginning
Stimulus
Yes
No
Subject fail to answer
Subject Talk
Talking Instruction
Coughing
X
“
+
No sign
T
TI
C
Chart Marking

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Mechanical Adjustment
Tearing of throat
Outside Noise
Sigh
Sniff
Sneeze
BURP
YAWN
Arrow
CT
OSN
S
SN
SZ
B
Y
Chart Marking


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

Deep breathing
Subject Laugh
Breathing Instruction
Repeat Question
Paper Jump
Ending
DB
L
BI
R
PJ
XX
Rule in Interpretation
There must be specific response hat
deviates from the subjects’ normal
tracing.
 It must appear in at least two or more
chart.

Thank you……….