POLYGRAPH LIE DETECTOR TEST

During the test, a trained interpreter uses a piece of equipment called a polygraph machine to measure subtle physiological reactions associated with lying. Lying causes a hormone called adrenaline to be released into the blood from the adrenal glands on the kidneys. Adrenaline causes your body to react in a variety of ways. We call this change in the body’s functions the “fight-or-flight” response.

Polygraph machines measure three physical factors associated with adrenaline. These are sweating, breathing, and heartbeat. Our device measures these through six different metrics: 

1. Pulse rate. This is how fast someone’s heart is beating. It’s measured in beats per minute (BPM). Elevated adrenaline levels cause the heart to beat faster.
2. Heart rate variability (HRV). This is a measure of how much the time between one heartbeat and another varies. It’s how we see whether someone’s heartbeat is speeding up or slowing down. HRV is especially useful in a lie detector test because it shows us precisely when someone begins to show a fight-or-flight response in the test.
3. Blood pressure. This is how much force someone’s heart is using to pump blood around your body. The heart uses more force when adrenaline levels are high than when adrenaline is at normal levels.
4. Skin temperature. Skin temperature directly correlates with how much adrenaline is in your blood. This is because adrenaline causes blood to be pumped around the body more quickly than usual. The increase in blood flow causes the skin to feel hot.
5. Breath control. Because adrenaline causes blood to be moved around the body at an elevated rate, breathing depth and frequency also increase to keep up. Our machine measures these changes in breathing to determine whether or not there is a stress response taking place.
6. Skin conductivity. When adrenaline causes someone’s bodily functions to speed up, body temperature increases. The body has to cool itself down when this happens, causing you to sweat. As well as water, sweat contains salts, making sweat conduct electricity more efficiently than usual moisture in the skin.

The polygraph machine uses tiny, painless electrical impulses to detect how well the skin is conducting electricity. The conductivity tells us how much someone is sweating and how their sweating changes in response to a question.

Our trained interpreters analyse the results of these tests on the body and pay attention to body language and certain vocal clues. They can use this to determine whether or not someone is giving a truthful answer to a question.

Some verbal signs of lying are helpful for you to tell whether someone might be lying to you, but they aren’t as valuable in a polygraph test. While bodily responses are things that they typically can’t control, the verbal signs of lying are subconscious attempts by the liar to ease their feelings of stress.

When we conduct a lie detector test, we want to ensure that a liar can’t ease these feelings. This need for a controlled test is why we limit our interrogation to yes/no questions. We only look for changes in vocal quality (the speed of the response and the pitch and tone of voice).