Lie Detection History of Lie Detection Current Methods What is the validity of lie detectors Legal Issues Can you beat a lie detector How to tell when someone is lying 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 2006 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 1 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 perfection 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