Voice stress analysis (VSA) and computer voice stress analysis (CVSA) are collectively a pseudoscientific technology that aims to infer deception from stress measured in the voice. The CVSA records the human voice using a microphone, and the technology is based on the tenet that the non-verbal, low-frequency content of the voice conveys information about the physiological and psychological state of the speaker. Typically utilized in investigative settings, the technology aims to differentiate between stressed and non-stressed outputs in response to stimuli (e.g., questions posed), with high stress seen as an indication of deception. [1]
The use of voice stress analysis (VSA) for the detection of deception is controversial. Discussions about the application of VSA have focused on whether this technology can indeed reliably detect stress, and, if so, whether deception can be inferred from this stress. [2] Critics have argued that—even if stress could reliably be measured from the voice—this would be highly similar to measuring stress with the polygraph, for example, and that all critiques centered on polygraph testing apply to VSA as well. [3] A 2002 review of the state of the art conducted for the United States Department of Justice found several technical challenges to the technology, including the same problem of determining deception. [4] When reviewing the literature on the effectiveness of VSA in 2003, the National Research Council concluded, "Overall, this research and the few controlled tests conducted over the past decade offer little or no scientific basis for the use of the computer voice stress analyzer or similar voice measurement instruments". [1] : 168 A 2013 paper published in Proceedings of Meetings on Acoustics reviewed the "scientific implausibility" of its principles and "ungrounded claims of the aggressive propaganda from sellers of voice stress analysis gadgets". [5] [6]
Confession made following a voice stress examination was allowed to be used as evidence in a Wisconsin case in 2014. [7]
In the case of the 1998 murder of 12-year-old Stephanie Crowe, confessions were made while three suspects were undergoing VSA, which were later found to be false by a judge. In 2005 the manufacturer of the VSA equipment later settled a lawsuit that alleged that it was liable for the harm the three suspects suffered. [8]
In a similar 2000 case in Washington state, Donovan Allen falsely confessed to killing his mother after failing a VSA test. He was acquitted 15 years later based on exonerating DNA evidence. [9]
George Zimmerman was given a VSA after he fatally shot Florida teenager Trayvon Martin in Sanford, Florida in 2012. [10]
Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.
"Truth serum" is a colloquial name for any of a range of psychoactive drugs used in an effort to obtain information from subjects who are unable or unwilling to provide it otherwise. These include ethanol, scopolamine, 3-quinuclidinyl benzilate, midazolam, flunitrazepam, sodium thiopental, and amobarbital, among others.
Voice analysis is the study of speech sounds for purposes other than linguistic content, such as in speech recognition. Such studies include mostly medical analysis of the voice (phoniatrics), but also speaker identification. More controversially, some believe that the truthfulness or emotional state of speakers can be determined using voice stress analysis or layered voice analysis.
The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound production in which the vocal folds are the primary sound source.
A polygraph, often incorrectly referred to as a lie detector test, is a device or procedure that measures and records several physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while a person is asked and answers a series of questions. The belief underpinning the use of the polygraph is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers; however, there are no specific physiological reactions associated with lying, making it difficult to identify factors that separate those who are lying from those who are telling the truth.
The Reid technique is a method of interrogation. The system was developed in the United States by John E. Reid in the 1950s. Reid was a psychologist, polygraph expert, and former Chicago police officer. The technique is known for creating a high pressure environment for the interviewee, followed by sympathy and offers of understanding and help, but only if a confession is forthcoming. Since its spread in the 1960s, it has been a mainstay of police procedure, especially in the United States.
In the branch of experimental psychology focused on sense, sensation, and perception, which is called psychophysics, a just-noticeable difference or JND is the amount something must be changed in order for a difference to be noticeable, detectable at least half the time. This limen is also known as the difference limen, difference threshold, or least perceptible difference.
Voice activity detection (VAD), also known as speech activity detection or speech detection, is the detection of the presence or absence of human speech, used in speech processing. The main uses of VAD are in speech coding and speech recognition. It can facilitate speech processing, and can also be used to deactivate some processes during non-speech section of an audio session: it can avoid unnecessary coding/transmission of silence packets in Voice over Internet Protocol (VoIP) applications, saving on computation and on network bandwidth.
A pitch detection algorithm (PDA) is an algorithm designed to estimate the pitch or fundamental frequency of a quasiperiodic or oscillating signal, usually a digital recording of speech or a musical note or tone. This can be done in the time domain, the frequency domain, or both.
A false confession is an admission of guilt for a crime which the individual did not commit. Although such confessions seem counterintuitive, they can be made voluntarily, perhaps to protect a third party, or induced through coercive interrogation techniques. When some degree of coercion is involved, studies have found that subjects with highly sophisticated intelligence or manipulated by their so called "friends" are more likely to make such confessions. Young people are particularly vulnerable to confessing, especially when stressed, tired, or traumatized, and have a significantly higher rate of false confessions than adults. Hundreds of innocent people have been convicted, imprisoned, and sometimes sentenced to death after confessing to crimes they did not commit—but years later, have been exonerated. It was not until several shocking false confession cases were publicized in the late 1980s, combined with the introduction of DNA evidence, that the extent of wrongful convictions began to emerge—and how often false confessions played a role in these.
In the law of criminal evidence, a confession is a statement by a suspect in crime which is adverse to that person. Some secondary authorities, such as Black's Law Dictionary, define a confession in more narrow terms, e.g. as "a statement admitting or acknowledging all facts necessary for conviction of a crime," which would be distinct from a mere admission of certain facts that, if true, would still not, by themselves, satisfy all the elements of the offense. The equivalent in civil cases is a statement against interest.
Throat singing refers to several vocal practices found in different cultures around the world. The most distinctive feature of such vocal practices is to be associated to some type of guttural voice, that contrasts with the most common types of voices employed in singing, which are usually represented by chest (modal) and head registers. Also, throat singing is often described as producing the sensation of more than one pitch at a time, i.e., the listener perceives two or more distinct musical notes, while the singer is producing a single vocalization.
Lie detection is an assessment of a verbal statement with the goal to reveal a possible intentional deceit. Lie detection may refer to a cognitive process of detecting deception by evaluating message content as well as non-verbal cues. It also may refer to questioning techniques used along with technology that record physiological functions to ascertain truth and falsehood in response. The latter is commonly used by law enforcement in the United States, but rarely in other countries because it is based on pseudoscience.
Grover Cleveland "Cleve" Backster Jr. was an interrogation specialist for the Central Intelligence Agency (CIA), best known for his experiments with plants using a polygraph instrument in the 1960s which led to his theory of primary perception where he claimed that plants feel pain and have extrasensory perception (ESP), which was widely reported in the media. These claims have been rejected by the scientific community.
Statement analysis, also called scientific content analysis (SCAN), is a technique for analyzing the words people use to try to determine if what they said is accurate. Proponents claim this technique can be used to detect concealed information, missing information, embedded confessions and whether the information that person has provided is true or false.
United States v. Scheffer, 523 U.S. 303 (1998), was the first case in which the Supreme Court issued a ruling with regard to the highly controversial matter of polygraph, or "lie-detector," testing. At issue was whether the per se exclusion of polygraph evidence offered by the accused in a military court violates the Sixth Amendment right to present a defense.
The ancient world lacked standardized practices of forensic science, which aided criminals in escaping punishment. Criminal investigations and trials relied on oaths, confessions and witness testimony. In a time when a distinction between science and such phenomena as religion, magic and superstition had not yet been made, some civilizations used practices such as the trial by ordeal to determine guilt or innocence.
John Augustus Larson was a Police Officer for Berkeley, California, United States, and famous for his invention of modern polygraph used in forensic investigations. He was the first American police officer having an academic doctorate and to use polygraph in criminal investigations. After a famed career in criminal investigation, he died of a heart attack in Nashville, Tennessee, at the age of 73.
Othello occurs when a suspicious observer discounts cues of truthfulness. Essentially the Othello error occurs, Paul Ekman states, "when the lie catcher fails to consider that a truthful person who is under stress may appear to be lying", their non-verbal signals expressing their worry at the possibility of being disbelieved. A lie-detector or polygraph may be deceived in the same way, by misinterpreting nervous signals from a truthful person. The error is named after William Shakespeare's tragic play Othello; the dynamics between the two main characters, Othello and Desdemona, are a particularly well-known example of the error in practice.
John J. Furedy was a Hungarian-born Australian and Canadian psychophysiologist and distinguished research professor of psychology at the University of Toronto, noted for his extensive empirical research into the unreliability of the polygraph test in lie detection and similar problems associated with biofeedback, as well as addressing contemporary issues concerning academic freedom.
[A] variety of factors could influence the presence or absence of the [voice pitch] microtremors, which are claimed to exist in our muscle control during speech production. It is clearly unlikely that a single measure such as that based on the computerized voice stress analyzer could be universally successful in assessing stress...it is not possible to cleanly separate the excitation signal into components due to emotion and those due to deception...a suspect under questioning would also display natural stress even if he were not guilty.