What is a LIE?

https://en.wikipedia.org/wiki/Lie

A lie is a statement that is known or intended by its source to be misleading, inaccurate, or false. The practice of communicating lies is called lying, and a person who communicates a lie may be termed a liar. Lies may be employed to serve a variety of instrumental, interpersonal, or psychological functions for the individuals who use them. Generally, the term "lie" carries a negative connotation, and depending on the context a person who communicates a lie may be subject to social, legal, religious, or criminal sanctions. In certain situations, however, lying is permitted, expected, or even encouraged. Because believing and acting on false information can have serious consequences, scientists and others have attempted to develop reliable methods for distinguishing lies from true statements.

Consequences

Once a lie has been told, there can be two alternative consequences: it may be discovered or remain undiscovered.

Under some circumstances, discovery of a lie may discredit other statements by the same speaker and can lead to social or legal sanctions against the speaker, such as ostracizing or conviction for perjury. When a lie is discovered, the state of mind and behavior of the lie teller (liar) is no longer predictable.

The discoverer of a lie may also be convinced or coerced to collaborate with the liar, becoming part of a conspiracy. They may actively propagate the lie to other parties, actively prevent the lie's discovery by other parties, or simply omit publicizing the lie (a secondary lie of omission).

Detection

Main article: Lie detection

Some people may be better "lie detectors" than others, better able to distinguish a lie by facial expression, cadence of speech, certain movements, and other methods. According to David J. Lieberman, PhD, in Never Be Lied to Again: How to Get the Truth in Five Minutes or Less in Any Conversation or Situation, these methods can be learned. Some methods of questioning may be more likely to elicit the truth, for instance: "When was the last time you smoked marijuana?" (a leading question) is more likely to get a truthful answer than "Do you smoke pot?" Asking the question most likely to get the information you want is a skill and can be learned. Avoiding vague questioning will help avoid lies of omission or vagueness.

The question of whether lies can reliably be detected through nonverbal means is a subject of some controversy.

Polygraph "lie detector" machines measure the physiological stress a subject endures in a number of measures while he/she gives statements or answers questions. Spikes in stress are purported to indicate lying. The accuracy of this method is widely disputed, and in several well-known cases it was proven to have been deceived. Nonetheless, it remains in use in many areas, primarily as a method for eliciting confessions or employment screening. Polygraph results are not admissible as court evidence and are generally perceived to be pseudoscience.
Various truth drugs have been proposed and used anecdotally, though none are considered very reliable. The CIA attempted to find a universal "truth serum" in the MK-ULTRA project, but it was an overall failure.
A recent study found that lying takes longer than telling the truth, and thus the time to answer a question may be used as a method of lie detection. However, it has also been shown that instant-answers can be proof of a prepared lie. The only compromise is to try to surprise the victim and find a midway answer, not too quick, nor too long.

Dr. Paul Ekman and Dr. Maureen O'Sullivan spent several decades studying people's ability to spot deception in a study called the Wizards Project. They studied police officers, psychologists, judges, lawyers, the CIA, FBI and the Secret Service. After studying nearly 20,000 people, they identified just over 50 people who can spot deception with great accuracy.

Dr. Freitas-Magalhaes developed the ForensicPsy and the Psy7Faces to read lies by facial expressions.