The truth of the lie detector

In 1978, in Ohio, a department store employee was shot and killed by a masked gangster. The police quickly arrested the suspect Fei Yi according to the clue. Fay screamed, but the police did not believe him and tested him with a polygraph. Fay failed both tests and he was found guilty. It was not until two and a half years later that the fierce mother came to confess, and Fay was able to elute the grievances.

Well, if you are arrested, but you have never committed a crime at all, but when all the evidence points to you, the prosecutor gives you a last chance to use a polygraph to check if you are innocent, if not Lie, acquitted. Then will you choose a lie detector?

The origin and prevalence of polygraphs

In fact, looking at the world, this assumption is not a hypothesis, but a real thing that often happens. This is because lie detectors have played an important role in human life for nearly a century.

At the beginning of the 19th century, American psychologist Marston found that the systolic blood pressure (also known as high pressure) of human blood vessels was related to lying. In 1921, Berkeley police officer Larsson invented the lie detector based on this theory. It was mainly used to measure blood pressure and respiratory frequency, and tried to calculate the possibility of lying according to the correlation. Later, Larsen’s student Keele improved the lie detector to make it portable, and added a new function, namely detecting skin electrical signal activity. This improvement has become the prototype of modern lie detectors.

The principle of this type of lie detector is that when people lie, people will show certain emotional and physiological reactions (such as nervousness and rapid heartbeat), so if these reactions can be detected, it means that the subject is lying. Then the lie detector came in handy. The San Francisco Police Department invited Larsson to test the suspect in a murder case. After Larsson’s test, the suspect was lying. Subsequently, other evidence also proved that the suspect was indeed lying.

As a result, the media began to vigorously promote this matter, with a large headline: “Science proves the crime of the suspect.” The San Francisco Police Commissioner also strongly recommended the lie detector to the public, and raised it to a moral level, stating that it could end the so-called “confession by torture”. “.

In addition to the police, as well as officials of the judicial system, they all advocate the use of polygraphs. I believe that this machine can solve some problems that cannot be solved by manpower alone. Therefore, the lie detector has a reputation for a while. Keeler, who is famous for his polygraph, also starred in the 1948 American film “The Anti-Case” and was performed in the real role of himself. The popularity of polygraphs today is still high, often appearing in key episodes of Hollywood movies.

Can a polygraph measure a lie?

From the invention and application of the polygraph, until today, nearly a century has passed, has it played its due role? The answer is pessimistic. Throughout history, the lie detector has not only played its role in identifying true and false, but on the contrary, it is almost everywhere. Regardless of the trial of murder suspects, the identification of national espionage, or the routine assessment of employees in the national security department, there are lie detectors in these areas, but the results are often flawed. One of the most notorious cases occurred in the 1980s.

There is a green river in the southern suburbs of Seattle, USA. Since 1982, police have found many bodies in the river, and some have become skeletons. The police then arrested Richway and listed him as a suspect. But Richway snorted, and finally passed the test of the polygraph (indicating no lying), the suspect was washed out of acquittal. At that time, DNA technology was not mature enough to be a conviction, but when the police released him, he kept samples of his hair and saliva. Until the technology matured in 2001, DNA analysis could be used as evidence, and the police arrested Richway again. This time, the ironclad was like a mountain. Richey had to bow his head and plead guilty. He finally confessed that he had killed 48 women and threw himself at the Green River in Seattle. (This incident was changed into a movie “Green River Killer”, which was released in 2005. ).

Afterwards, Richway explained how he passed the test of the polygraph in the past, because he was physically and mentally relaxed, and he had no worries in his heart, and he answered the question simply and truthfully. When the murderer is still at the stage of the suspect, the lie detector has eluted the suspect (he killed a lot of people in the past ten years after the release), which is really unfounded! In this case, if it is a tragedy for a few people, then there is another situation that is a tragedy for the whole country.

The lie detector is not only used in criminal cases, but also often used in intelligence work, but it does not play any role. The US Central Intelligence Agency (CIA) has an employee, Ames, whose father is also an intelligence officer. Ames University has not worked as a part-time job in the Intelligence Bureau. After graduation, he has been working in the Intelligence Bureau for more than 30 years. When he was found to be engaged in espionage in 1994, he had secretly transmitted intelligence to Russia (the Soviet Union) for nine years. During this period, the CIA conducted routine tests without interruption, using lie detectors to test employee loyalty, but Ames could easily pass the test of the lie detector every time. The secret information he transmitted during the past nine years has caused huge losses to the United States.

Why is the polygraph not accurate?

Strictly speaking, the lie detector does not detect lies, but detects physiological reactions such as blood pressure, heartbeat, and breathing, and then infers whether the subject is lying. Under certain conditions, lying can indeed lead to elevated blood pressure, rapid heartbeat and breathing, and physiological reactions such as sweating of the skin (such as the palm of the hand), but in turn, these physiological reactions occur, but not necessarily caused by lying.

First, scientific research shows that these physiological responses are caused by lying-induced stress, with a probability of only about 50%. Other psychological stresses and embarrassing emotions can cause similar physiological reactions, and sometimes even the tone of the interrogator’s tone can cause similar reactions in the subject. If the suspect is innocent, then the lie detector will be “falsely sentenced” to lie, thereby aggravating the suspicion and even being convicted.

Second, sociological studies have shown that certain groups are often stigmatized if they are discriminated against by society (such as “the thief’s son is always a thief”), then one of these groups is once considered a suspect, even if he It is an honest and honest person. When confronted with interrogation and lie detection, there will be tension and specific physiological reactions. This reaction is similar to the standard that the lie detector is to detect.

Third, some people are naturally calm, and there is no tension that normal people have. This is also a spiritual problem. A typical example is Ricky’s, which clearly lacks normal levels of anxiety compared to normal people. That is to say, this type of person is almost not anxious, and does not suffer from physiological reactions such as rapid heartbeat and shortness of breath due to nervousness, so of course he does not cause the “eye-catching” of the polygraph.

In addition, as long as you understand the principle of the polygraph, and then a little training to master some skills, most people can “handle” the polygraph and easily pass the test. For example, continuous and even breathing, regardless of the problem, always keep the respiratory rate consistent, 15 to 30 times per minute, and so on.

Why is the polygraph popular for a long time?

Although there are so many drawbacks, the lie detector is still in service for a long time. It is commonly used in US government agencies to assess and select employees, while federal law enforcement agencies basically use it as an interrogation tool. In addition, in Israel and Canada, lie detectors have also been widely used.

The first is the reason for institutionalization. After all, since the birth, the polygraph has received strong support from the official (police) and has been lobbying the public for nearly 100 years. In the police and judicial departments, lie detectors have penetrated into the trial system, forming a culture of interrogation that is deeply rooted. Once institutionalization is formed, it is difficult to change.

This is very similar to the “nine-step interrogation method” that the US police often use. Developed in the 1940s, the nine-step interrogation method is a method in which interrogators use nine steps to interrogate to obtain confessions. This method is considered in great detail for each interrogation session and is designed to enable suspects to be in specific chat situations. Next, unconsciously talk about the facts of the crime, thus helping the police to obtain confessions. But this technique is also flawed. It is easy to produce temptations and indirectly succumb to good people. The US Supreme Court has issued a judicial interpretation to warn this skill, but it still cannot stop the police from using it.

The second reason is the promotion of popular culture. In the entertainment industry, from the 1948 movie “Anti-Case”, the lie detector was frequently on the mirror, and the related topics have not been broken. The use of lie detectors in the film can make the fate of the characters appear suspense and make the development of the plot more ups and downs, which is very attractive to the audience. Therefore, the film production company and the media have continuously introduced the plot of the lie detector to increase the movie sales rate.

So the polygraph appeared in a large number of people’s vision, which indirectly increased its reputation. The more topics of lie detectors in movies and media, the more police and government agencies use them. Therefore, popular culture has played a role in fueling the use of polygraphs, but from a more precise point of view, it is better to say that the commercial interests of the entertainment industry have promoted the polygraph.

The third reason is the positioning of the polygraph. In fact, for nearly a century, polygraphs have never met the standards adopted by the court as evidence. In 1998, the US Supreme Court slightly loosened the use of polygraphs, but did not receive widespread support. Instead, it is widely used in police interrogation of suspects, intelligence bureau interrogation, routine appraisal staff, and public entertainment. In other words, the polygraph is never a forensic tool, but is used as a means of interrogation, and is a powerful and effective tool that represents the authority of the interrogation authority.