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Allah Almighty tells us in the Qur'an about signs of lying in face and voice of the liar, let us read ...

Face detection

Researchers have noticed some facial changes when speaking. Thus, they experienced it by photographing a man telling truth, and just in the lying moment, specific features appear on his face, which are different from those appearing in the truth state. But, these features are very rapid that human being eye cannot see.

"Polygraph lie detectors are notoriously unreliable: 10 percent of liars pass, and 20 percent of truth tellers fail. But the real truth is written all over your face "says cognitive scientist Marian Stewart Bartlett, at the Institute for Neural Computation in San Diego.
Now there's a way to catch liars in the act. Bartlett and several colleagues at the Salk Institute have developed a high-speed computer program that analyzes videotapes to automatically detect a subject's micro expressions. The program superimposes a grid over a baseline black-and-white photograph of the subject's face devoid of all expression. Any change in expression, no matter how subtle or fast, registers on the grid as a departure from baseline. For example, if eyebrows lower in anger, they leave their neutral position - a movement documented by the computer. "The method it uses," Bartlett says, "is based on the way the brain interprets vision." The neurons that deal with vision each look at a different part of an image, and the brain assembles the information.

Every emotion a person feels elicits an involuntary facial expression, but often just for a split second. When someone tries to cover those emotions, the expression passes so quickly most people miss it.
Allah tells us about this scientific fact as He Almighty says about atheists who denies the Qur'an: (And when Our Clear Verses are recited to them, you will notice a denial on the faces of the disbelievers!) {Sûrat Al-Hajj - The Pilgrimage-verse72}.

This is a clear link between the humanfeelings and what appears on their faces. Glory to Allah!!!!!

Also, scientists say that any repeated action by human becomes part of his or her facial expressions, so Allah almighty says about the believers: (Muhammad is the Messenger of Allah, and those who are with him are severe against disbelievers, and merciful among themselves . You see them bowing and falling down prostrate (in prayer), seeking Bounty from Allah and (His) Good Pleasure. The mark of them (ie of their Faith) is on their faces (foreheads) from the traces of (their) prostration (during prayers)) {Sûrat Al-Fath-The Victory-verse 29}.

Also, in the day of resurrection we will distinguish between believers and disbelievers from their faces as Allah almighty say: (Verily, Al-Abrar (the pious who fear Allah and avoid evil) will be in delight (Paradise) * On thrones, looking (at all things) * You will recognize in their faces the brightness of delight.) {Sûrat Al-Mutaffifîn-Those Who Deal in Fraud-verse22-24}.

But Hypocrites and disbelievers who are trying to hide their hating for believers in this life, will not be able to hide that feeling in front of Allah Almighty and all people in the day of judgment as He says about them: (On the Day when their faces will be turned over in the Fire, they will say: "Oh, would that we had obeyed Allah and obeyed the Messenger (Muhammad).") {Sûrat Al-Ahzâb-The Confederates-verse66}.

Voice detection

Also voice-stress analysis, an alternative to the polygraph as a method for lie detection, is already widely used in police and insurance fraud investigations. Now, however, it is being touted as a powerful and effective tool for an array of new applications - everything from the screening of potential terrorists in airports to catching wayward spouses in messy marital disputes.

Despite its booming popularity, a number of federally sponsored studies have found little or no scientific evidence to support the notion that existing voice-stress technologies are capable of consistently detecting lies and deceptions.

The Truster hand-held "Emotion Reader" is one of many commercial products that claim to detect lies and deception using voice-stress analysis.

"Voice-stress analysis is fairly effective in identifying certain variations in stress levels in human speech, but high levels of stress do not necessarily correlate with deception," said Mitchell S. Sommers, an associate professor of psychology in Arts & Sciences at Washington University in St. Louis.

"It may someday be possible to refine voice-stress analysis so that it is capable of distinguishing among various sources of stress and accurately identifying those that are directly related to deception." He added.

In theory, voice-stress analysis works by measuring slight inaudible fluctuations in the human voice known as "micro-tremors." Voice-stress analysis systems, which generally include a microphone, tape recorder and related computer analysis equipment, are designed to recognize micro-tremor patterns that indicate when a speaker delivers words under stress, and specifically when those moments of stress are generated by an attempt to lie or deceive. Voice patterns are analyzed, graphed and displayed on a computer screen.

So, AllahAlmighty says about those Hypocrites who say what is against their beliefs: (Had We willed, We could have shown them to you, and you should have known them by their marks, but surely, you will know them by the tone of their speech! And Allah knows all your deeds.) {Sûrat Muhammad or Sûrat Al-Qitâl-verse30}.

O 'Allah, make us from the sincere people in life and in the hereafter, Allah says about those people: (And whosoever submits his face (himself) to Allah [ie (follows Allah's Religion of Islamic Monotheism), worships Allah (Alone) with sincere Faith in the (1) Oneness of His Lordship, (2) Oneness of His worship, and (3) Oneness of His Names and Qualities], while he is a Muhsin (good-doer ie performs good deeds totally for Allah's sake without any show-off or to gain praise or fame etc. and does them in accordance with the Sunnah of Allah's Messenger Muhammad), then he has grasped the most trustworthy hand-hold [La ilaha ill-Allah (none has the right to be worshipped but Allah)]. And to Allah return all matters for decision) {Sûrat Luqmân-verse22}.

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May be that's why Allah warns the Believers that while having friends among the non-Believers - never trust them blindly.