Lie Detection
•History of Lie Detection
•Current Methods
•What is the validity of lie
•Legal Issues
•Can you beat a lie detector?
•How to tell when someone is
•How to lie
History of Lie Detection
Greeks would ask questions and “feel the subject’s pulse.”
Torture as a means of interrogation:
– Romans used crucifixion.
– Strappado was a means of medieval inquisition torture which
would dislocate joints. The rack would stretch the victim’s joints
to breaking point. Red hot pinchers would be applied…
– Modern: Leave a victim with no visible damage.
In 1948, following the horrific abuses of World War II, the
General Assembly of the United Nations inserted the
prohibition against torture in the landmark Universal
Declaration of Human Rights. Article 5 states: "No one shall
be subjected to torture or to cruel, inhuman or degrading
treatment or punishment." The prohibition against torture is
well established under customary international law as
jus cogens.
The Supreme Court in 1963 ruled that a confession
extracted under “truth serum” – drugs such as sodium
pentothal, sodium amytal, and scopolamine - violated a
defendant's constitutional right against self-incrimination.
Should torture/ “truth serum” be permitted if its use
would save lives or benefit society?
Current Methods
Modern polygraphy: uses physiological changes in the peripheral nervous system
(PNS) measure deception
1. Skin conductance changes (sweating)
2. Blood pressure
3. Respiration
4. Heart rate
Facial Micro-expressions (developed by Paul Ekman)
• It would have the advantage of not requiring any obvious intervention with the
subject. Could be used secretively by videotaping.
“Neurotechnological Lie Detection” (NTLD):
• Measurements of blood flow or electrical impulses in the brain to identify distinct
indicators of deceptive communication.
• Measure lying more directly by measuring brain activity rather than second-order
indicators like pulse or respiration.
Advantages over polygraph testing:
• Fear or other strong emotions may affect physiological responses and thus may
confound the data in polygraphy.
• Polygraphy requires trained experts to read the graphs, while NTLDs would only
require computers.
• Does this mean that NTLDs are reliable evidence in court?
Two categories of NTLD
1. Blood Flow Patterns
• By studying blood flow patterns during deception and
comparing them to blood flow patterns during nondeception in similar situations, researchers can learn
which regions of the brain are activated when people
are lying.
• Functioning Magnetic Resonance Imaging (fMRI) is
currently the most commonly used method for
measuring blood flow in the brain. Images are
constructed based on blood-oxygenation-level
dependent (BOLD) contrast. When a brain region is
more metabolically active, there is a local increase in
MR signal or BOLD contrast. When people lie, the
anterior cingulate cortex is activated. No Lie MRI
started offering its fMRI-based lie detection services in
• Near-infrared spectroscopy (NIRS) focuses on
activity in the prefrontal cortex and provides a way to
measure changes in blood flow without the complex
apparatus of an MRI machine. The basis of the
technology is the measurement of how near infrared
light is scattered or absorbed by various materials.
Small devices are attached to the subject’s skull, which
shine near-infrared light through the skull and into the
brain. This scattered laser light is picked up by sensors
on the subject’s skull. The pattern of scattering reveals
the pattern of blood flow through the outer regions of
the brain.
• Thermal imaging: When people lie their eyes give off
more heat.
Patterns of Recognition
Use event related potentials (ERPs) through electroencephalogram
(EEG) to identify patterns of recognition for the wave pattern of the
P300 wave. With EEG, the researcher uses electrodes placed on
the subject’s scalp to detect and measure patterns of electrical
activity emanating from the brain.
“Brain fingerprinting” attempts to discern whether a person has
knowledge of a particular event or an image stored in his brain. The
P300 wave occurs when a subject recognizes information or a
familiar stimulus. It is the only technique considered for admission
into evidence.
Is this ethical?
• Because these methods rely on correlations to determine lies, are
they reliable?
• Should personal privacy be sacrificed for the better of society
because NTLDs could serve forensic, security, and military
purposes? Is personal privacy even being invaded?
• What about the self-incrimination clause of the Fifth Amendment
that states that no person “shall be compelled in any criminal case to
be a witness against himself?”
Garnering the evidence vs. entering the suspect’s mind is violating
• Brain imaging and brain fingerprinting require clear testimonial
response from the suspect, such as pressing a button. Is this the
same as blood or hand writing samples used to solve a crime?
• Previously, in order for the contents of a person’s mind to be
exposed, he had to communicate that content actively, whether by
speaking, writing, gesticulating, or some other deliberate means. Is
this still considered communicating?
What is the validity of lie detectors?
United States v. Scheffer (1998):
A host of studies show that polygraph testing shows 85% to 90% accuracy while critics state that it
is 70%.
More likely to show innocent people guilty than vice versa.
1. False positive
Leads to an incorrect accusation against the communicator. These may be more serious than
false negative.
2. False Negative
The "liar" gets away with the lie. This has been the traditional focus
for assessment of the accuracy of a communication.
“Polygraph tests can discriminate lying from truth telling at rates well above chance but well below
Hence, for the control question theory to be valid, two assumptions must hold. The first requires
innocent individuals to be more responsive to control than relevant questions. The second requires
guilty persons to respond more intensely to relevant than control questions. The plausibility of both
of these assumptions can be easily challenged.
The notion that guilty suspects will necessarily respond more strongly to relevant than control
questions is unlikely for several reasons.
The notion that a guilty suspects will necessarily respond more strongly to relevant than control
questions is unlikely for several reasons.
If a guilty person passed the test, there would be no confession to guilt and that the test was
wrong? So how accurate are the studies don’t for lie detection?
How can lie detection be verified as accurately recording the truth or not?
Brain fingerprinting: Is this an accurate method when people have “memory problems”? What if
someone is telling the truth but is factually wrong?
There is not a 100% accurate way lie detection method
Legal Issues
Frye vs. United States: The Frye standard is a legal precedent regarding
the admissibility of scientific examinations or experiments in legal
precedings. To meet the Frye standard, scientific evidence presented to
the court must be interpreted by the court as "generally accepted" by a
meaningful segment of the associated scientific community.
Daubert v. Merrell Dow Pharmaceuticals (1993): The Daubert standard is
a legal precedent regarding the admissibility of expert witnesses’
testimony during legal proceedings.
United States v. Scheffer (1998): Military Rule of Evidence 707 (“failure to
take, or taking a polygraph examination shall not be admitted into
evidence”) v. 6th Amendment (right to defend oneself)
After United States v. Scheffer, most jurisdictions exclude all polygraphic
evidence. However, two federal circuits held that polygraphic tests could
be admitted on a case-by-case basis and New Mexico admitted
polygraphic evidence.
The Employee Polygraph Protection Act of 1988:
• Established guidelines for polygraph testing and imposed restrictions on
private employers such as companies and corporations
• Does NOT affect public employers such as police agencies or other
governmental institutions.
• Should public employers be trusted more than private employers?
Legal Issues cont.
Iowa v. Harrington
• a post-conviction relief action undertaken 26 years after a
murder; EEG responses to probes such as “across
street,” “parked cars,” and “weeds and grass,” all of which
related to the crime scene, showed that he had no
memory of the crime; the district judge ultimately did not
find the evidence persuasive
By allowing scientific testimony regarding truthfulness
into evidence, is the court invading the purview of the
Can you test defendants? Can you test nondefendant
Bias detection: can we test a jury to see if they will be
Should lie detection methods be used in courts?
Can you beat a lie detector?
There are three basic types of questions you will be asked: relevant, irrelevant, and
Don’t admit anything relevant.
Say only what you need to. “Yes” or “No” answers
Maintain a normal breathing rate of 15-30 breaths per minute but alter it during control
Bite your tongue. Bite the side of your tongue hard enough to cause pain.
Insert a small nail or tack in the toe area of your shoe and press down on this during the
control questions to elicit a pain response.
Contract your anal sphincter muscle when a control question is asked (pressuresensitive seat pads).
Your first impulse will be to try to conceal all emotion, but that is exactly what not to do.
The physical effort required to conceal emotion shows up and could often be detected
without a machine. So, in beating the lie detector, intensify them as much as possible.
To confuse the test from the start, you might tense your muscles when the rubber is
wrapped around your arm.
The way to beat the association test is simply to blurt out the first word you think of in
association. The body was found in a park, so when one of the key words given you is
"park," naturally the first word you think of, whether you're guilty or innocent, is "murder."
Seeing that you appear to be not afraid of his machine, the operator will be naive
enough to think you innocent.
How to tell when someone is lying
General Verbal Responses
May take longer to start answering
May answer to quickly or before the question is completed
Often ask the questioner to repeat the question or they repeat it themselves
Overly polite or apologetic dialog
Persistent complaints
Unnatural silence
The Behavioral Clusters of Deception
Deceptive people follow certain behavioral patterns.
- Macro Patterns General Behaviors:
Increased discomfort and anxiety, hostility, unmerited anger towards you, persistent evasiveness, resistance
Early signs of extreme rigidity followed by alternating stiffness and relaxation. Hands, legs, objects put in front of body to
form a barrier (folding arms, crossing legs, etc.). Feigned lack of interest. Posture changes caused by topic changes. Not
facing you. Distancing or leaning away from you.
Gestures and Movements:
Rubbing the forehead near the temple region. Squeezing the face, rubbing the neck, or stroking the back of the head with
the hand. Using fewer hand movements to illustrate their actions than usual. Movement away from you. Lip licking and
hard swallowing. Wringing hands. Hiding the eyes
- Micro Patterns -expressed on the face
General Expressions:
Averting the eyes. Focusing the eyes - some will try to stare down to show control. (A truthful person stares only half the
time on average). Face whitening.Face flushing.
Eye-Accessing Cues
By the direction of where the person’s eyes are looking, you can determine whether they are using vision, sound or
kinesthetic (feeling) to trigger their thinking.
Keep in mind that this is reversed for left-dominant people (left handers). So before you can use this, be aware of which
of their sides is the dominant one.
Eye Movement
How to lie
• The first thing you do when lying is to tell the truth -- not the whole
truth, but just enough to make the lie itself seem true. If you sense
that someone else suspects you of lying, admit to something small or
untrue. Think of some specific true thing (place, person, event, story)
that your lie will fit into and use those details if you are questioned.
This gives you a bank of specific details to draw on so you don't have
to keep making things up as you go along.
• The trick is convincing your sub-conscious mind that you're telling the
truth. An example of this may be, "Did I wreck the car? Well, I drove it
into a wall. So, the wall wrecked the car. I just moved it!”
• Look the person you are lying to in the eye. Don't look around. Try
making your eyes go big and letting your mouth hang open a little for
an innocent/shocked look.
• Never forget about your lie, and treat it like it actually happened.
Mention it in conversations the way you would if it was true. Silence
about a certain subject can arouse suspicion, especially in retrospect.
• Use named, recognizable people.
But most importantly…
Always tell the
You’re Detective Poly.
1. Start with invasive CONTROL questions to begin to recognize
his/her regular behavior.
YOU: What class do you have tomorrow?
YOU: Who is your favorite musician? What’s the favorite concert you
have ever been too?
YOU: What restaurants do you recommend? What kind of food do they
2. Now lets get to the truth!! Here are some suggested ?s…Feel free to
ask different ones, but the key is to probe.
YOU: Have you ever lied to your best friend? What did you say to
YOU: Since you’ve been at Vanderbilt have you washed your bed
YOU: Where were you born? What was the name of the hospital?
YOU: In the past month, have you deliberately not answered
someone’s phone call? Who was the person?
You’re Suspect Suspicion
1. You will be asked a set of control
questions first that you must answer
truthfully for the experiment
2. Let the lying begin! (Note: You may
answer all of the questions right or all
wrong if you want. This might throw
Detective Poly off.)
3. Evaluation from Detective Poly
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