The polygraph, commonly known as a lie detector, is a crucial forensic psychology tool used to detect deception. By measuring physiological changes like heart rate, blood pressure, and breathing, the polygraph helps determine if someone is telling the truth. This blog will explore how the polygraph works, its role in solving crimes, and a notable case in India where it was instrumental.

How the Polygraph Works (Forensic Psychology Tool)

The polygraph detects lies by recording changes in the body’s physiological responses when a person answers questions. If a person lies, their body may exhibit signs of stress, such as an increased heartbeat or rapid breathing. The polygraph records these signs, assisting investigators in determining the truth. This tool is often used in criminal investigations to gather essential information

There are four components of polygraph:-

Pneumograms:

1. Abdominal Pneumogram: Tube for the abdominal region

2. Thoracic Pneumogram: Tube for lungs region

Galvanometer: Electrodermal conductivity

P-Gauge: Body Movement 

Sphygmomanometer/ Oximeter: Blood Pressure or Oxygen Levels

The Nithari Killings: A Case Solved with the Polygraph

In 2006, the Nithari killings in Uttar Pradesh shocked India. Numerous children and women went missing, leading to the arrest of Moninder Singh Pandher and his servant, Surinder Koli. During the investigation, both men underwent polygraph tests. Koli’s polygraph results, combined with other evidence, played a critical role in securing his confession. This case highlights how the polygraph can be a powerful tool in solving crimes.

Uses and Limits of the Polygraph

The polygraph is used in various situations. Law enforcement agencies use it to detect lies during investigations. It is also sometimes used by companies during hiring processes and in legal cases. However, the polygraph is not infallible; factors like nervousness or health conditions can affect the results. Thus, it is typically used alongside other investigative methods.

Conclusion:

The polygraph remains a vital forensic psychology tool that aids in detecting deception by measuring physiological changes. Though not perfect, its effectiveness in cases like the Nithari killings demonstrates its significant role in criminal investigations.