Sunday, November 30, 2008

Lie Detectors: How Truthful Are These Devices?

The modern lie detector / polygraph test has said to have been used in proving guilt or innocence in offences as varied as petty theft to witnessing an “alleged” alien abduction. But are these machines truthful?

By: Vanessa Uy

The high-profile use of lie detectors / polygraph test machines in the US justice system range from the proving the guilt or innocence of rogue CIA agents to the credibility of alien abduction witnesses and victims. Even though majority of us know that these devices are used to determine whether the subject being tested is telling the truth or not, but can the machine irrefutably determine the guilt or innocence of the “test subject”?

In reality, polygraph test devices – or as it is more famously known colloquially as lie detector machines – measures how the subject reacts to the set of questions being asked physiologically. Whether the subject is lying or not is usually determined by the person supervising the test basing on the resulting measurements. One of the few manufacturers of purpose-built polygraph devices is the Lafayette Instrument Company in Lafayette, Indiana. The manufacturing firm makes polygraph devices that costs around 12,000 US dollars each. A typical polygraph – usually classified as a 4-pin device - has several modules that measures galvanic skin response – or GSR, the breathing rate via a pneumosensor, and the heart rate and blood pressure.

Newer digital / PC-based polygraph devices now exist (and are even way cheaper), but these are not as accurate as a purpose-build polygraph device. Though PC-based 4-pin polygraph devices has a proviso to store / save data digitally. Even though these types of polygraph does very well in their intended roles like measuring GSR, heart rate, blood pressure, breathing rate, etc. They cannot yet irrefutably determine the guilt or innocence of the person under test. That's why, lie detectors / polygraph test data are usually inadmissible in criminal court proceedings where the polygraph data is used to determine the guilt or innocence of the accused.

The latest form of these “lie detector” devices is called Brain Fingerprinting, which is touted to be more accurate than the current polygraph test devices in use. Developed by Dr. Laurence Farwell – a Seattle-based neuroscientist, Brain Fingerprinting is a radically new type of “lie detector” that has proven to have a more than 90% certainty rate in determining whether the subject is telling the truth or not. The newfangled system locks on to the P300 murmur response of the brain when the test subject is asked a well-selected roster of pertinent questions about the crime. The test subject’s brain response / brain wave patterns is measured via a sensor cap. At present, brain fingerprinting test results is not yet admissible as evidence in majority of US courts.

Despite of the advances in lie detection technology over the years, the US justice system is still weary of accepting polygraph test / lie detection data as evidence because the test results are open to interpretation. And lie detection devices somewhat violate the plaintiff’s constitutional rights against self-incrimination when such devices are used in criminal trial proceedings. Plus, it’s been proven that polygraph test devices / lie detectors are not infallible. Former CIA double agents / rogue agents Aldrich Aames and Howard Woodward “aced” their polygraph tests during the 1980’s even though the other evidence presented in their trials proved their guilt. Howard Woodward even manage to escape into the Iron Curtain more than 20 years ago and his whereabouts today still remain unknown despite the Cold War ending for almost two decades.