The truth about lie detectors

  In 1978, in Ohio, the United States, a department store employee was shot and killed by a masked criminal. The police quickly arrested the suspect Faye based on clues. Faye called wrong, but the police did not believe him and tested him with a polygraph. Faye failed two tests, so he was found guilty. It wasn’t until two and a half years later that the murderer’s mother came to confess that Faye was able to get rid of his grievances.
  So, if you are arrested, and in fact you have never committed a crime, but when all the evidence points to you, the prosecutor will give you the last chance to use a polygraph to test whether you are innocent, if not If you lie, you will be acquitted. Will you choose a polygraph at this time?
  Polygraph origin and prevalence of
  fact, throughout the world, this assumption is not a hypothesis, but the real thing often happens. This is because polygraphs have played an important role in human life for nearly a century.
  At the beginning of the 19th century, American psychologist Marston discovered that the systolic blood pressure (also known as high pressure) of the human blood vessels is related to lying. In 1921, American Berkeley police officer Larson invented a polygraph based on this theory, which was mainly used to measure blood pressure and breathing rate at the time, trying to calculate the possibility of lying based on the correlation. Later, Larson’s protégé Keeler made improvements to the polygraph to make it easy to carry, and a new feature was added to detect electrical skin signal activity. This improvement has become the prototype of modern polygraphs.
  The principle of this kind of polygraph is that when people lie, people will show certain emotional and physiological reactions (such as nervousness, rapid heartbeat), so if these reactions can be detected, it can indicate that the subject is lying. Then the polygraph came in handy. The San Francisco Police Department invited Larson to test a suspect in a murder case. After the test, Larson determined that the suspect was lying. Subsequently, other evidence also proved that the suspect was indeed lying.
  As a result, the media began to vigorously publicize the matter, with a large headline: “Scientifically prove the crime of the suspect.” The San Francisco Police Commission also strongly recommended the polygraph to the public and raised it to a moral level, declaring that it could end the so-called “torture of confessions.” “.
  In addition to the police, there are officials from the judicial system who all advocate the use of a polygraph, believing that this machine can solve some problems that cannot be solved by humans alone, so for a while, the polygraph became famous. Keeler, famous for his polygraph, also starred in the 1948 American movie “Counter Case”, and played his true role as himself. Today, the popularity of polygraphs is still very high, often appearing in key plots of Hollywood movies.
  Can a lie detector detect a lie?
  Nearly a century has passed since the invention and application of the polygraph, has it played its due role? The answer is very pessimistic. Throughout history, polygraphs have not only failed to distinguish true from false as they should be, on the contrary, there are almost “remnants” everywhere. Whether interrogating criminal suspects, identifying national spies, or routinely assessing employees of national security departments, polygraphs are used in these areas, but the results are often full of errors. One of the most notorious cases occurred in the 1980s.
  There is a green river in the southern suburbs of Seattle in the United States. Since 1982, police have found many bodies in the river, some of which have become skeletons. Then the police arrested Ridgway and listed him as a suspect. But Ridgway said he was wronged, and finally passed the test of the polygraph easily (indicating that he did not lie), and was acquitted. At that time, DNA technology was still immature and could not be used as evidence of conviction, but when the police released him, he kept samples of his hair and saliva. Until 2001, when the technology was mature, DNA analysis could be used as evidence in court, and the police arrested Ridgway again. This time, the evidence was so strong that Ridgway had to bow his head and plead guilty. He finally confessed that he killed 48 women and threw their bodies in Seattle’s Green River (this incident was changed into the movie “The Green River Killer”, which was released in 2005 ).
  Afterwards, Ridgway explained how he passed the polygraph test because he was relaxed physically and mentally, without any worries, and answered the questions “simple and truthfully”. When the real culprit was still at the stage of suspects, the polygraph eluted his suspicion (he killed a lot of people more than ten years after his release), which is really embarrassing! If this situation is a tragedy for a few people, then there is another situation that is a tragedy for the entire country.
  The polygraph is not only used in criminal situations, but also often used in intelligence work, but it also has no effect. The United States Central Intelligence Agency (CIA) has an employee, Ames, whose father is also an CIA officer. Before graduating from Ames University, he worked part-time in the Intelligence Bureau, and stayed there after graduation. He has been working in the Intelligence Bureau for more than 30 years. He had been secretly sending intelligence to Russia (Soviet Union) for 9 years when he was discovered to be working as a spy in 1994. During this period, the CIA continuously carried out routine tests, using a polygraph to test the loyalty of employees, but Ames could easily pass the polygraph test every time. The classified information he sent in the past nine years has caused huge losses to the United States.
  Why is the polygraph inaccurate?
  Strictly speaking, the polygraph does not detect lies, but detects physiological reactions such as blood pressure, heartbeat, and respiration, and then infers whether the subject is lying. Under certain conditions, lying can indeed cause physiological reactions such as increased blood pressure, rapid heartbeat and breathing, and sweating of the skin (such as the palm of the hand), but in turn, these physiological reactions in people are not necessarily caused by lying.
  First of all, scientific research shows that the probability of these physiological reactions caused by lying caused by tension is only about 50%. Other psychological tensions and embarrassing emotions can also cause similar physiological reactions, and sometimes even the tone of the interrogator can cause similar reactions to the subjects. If the suspect is innocent, he will be “misjudged” as a lie by the polygraph at this time, thereby increasing the suspicion and even being convicted.
  Second, sociological research shows that if certain groups are discriminated against by society and are often stigmatized (for example, “the son of a thief is always a thief”), once a member of these groups is regarded as a suspect, even if he An upright and honest person, when facing interrogation and polygraph tests, he will also experience nervousness and specific physiological reactions, which are very similar to the standards tested by a polygraph.
  Third, some people are naturally calm and do not have the tension that normal people have. This is also a mental problem. A typical example is Ridgway. Compared with normal people, he obviously lacks the normal level of anxiety. In other words, this type of person hardly feels anxious, and will not have physiological reactions such as rapid heartbeat and shortness of breath due to tension, so of course he will not cause the “eyes” of the polygraph.
  In addition, as long as you understand the principle of the polygraph, and with a little training to master some skills, most people can “handle” the polygraph and pass the test easily. For example, breathe continuously and evenly, no matter what problem you are facing, always keep your breathing rate consistent, 15-30 times per minute, and so on.
  Why can the polygraph be popular for a long time?
  Although there are so many drawbacks, the polygraph is still in long-term “service” until now. It is commonly used in US government agencies to evaluate and select employees, while federal law enforcement agencies basically use it as an interrogation tool. In addition, in Israel and Canada, polygraphs have also been widely used.
  The first is the reason for institutionalization. After all, since its birth, the polygraph has received strong official (police) support and has been lobbying the public for nearly 100 years. In the police and judicial departments, polygraphs have infiltrated the interrogation system, forming a culture of interrogation and deep-rooted. Once institutionalization is formed, it is difficult to change.
  This is very similar to the “nine-step interrogation method” often used by the US police. The nine-step interrogation method was developed in the 1940s. It is a method by which interrogators use nine steps to interrogate to obtain confessions. This method considers every interrogation link in great detail, and aims to make criminal suspects in specific chat situations. Next, unconsciously talk about the facts of the crime to help the police obtain a confession. But this technique is also flawed. It is easy to induce confession and indirectly betray good people. The Supreme Court of the United States issued a judicial interpretation to guard against this technique, but it still cannot stop the police from using it.
  The second reason is the promotion of popular culture. In the entertainment industry, since the 1948 movie “Counter Case”, polygraphs have been frequently on the camera, and topics related to this have not been interrupted so far. The use of a polygraph in the movie can make the character’s fate appear in great suspense and make the plot development more ups and downs, which is very attractive to the audience. Therefore, film production companies and the media continue to introduce plots of polygraphs to increase movie sales.
  As a result, a large number of polygraphs appeared in people’s field of vision, which indirectly enhanced its reputation. The more topics about polygraphs appear in movies and media, the more police and government agencies use them. Therefore, popular culture has contributed to the use of polygraphs, but from a more precise point of view, it is the commercial interests of the entertainment industry that promote the use of polygraphs.
  The third reason is the positioning of the polygraph. In fact, for nearly a century, the polygraph has never reached the standard adopted by the court as evidence. The U.S. Supreme Court’s use of polygraphs was slightly relaxed in 1998, but it did not receive widespread support. On the contrary, it has been widely used in police interrogation of suspects, intelligence bureau interrogation of spies, routine examination of employees, and popular entertainment programs. In other words, the polygraph has never been a tool for forensics, but used as an interrogation tool, and it is powerful and effective, representing a tool of the authority of the interrogation agency.