Kathmandu, January 21

The Metropolitan Police Office has conducted 42 polygraph tests on as many suspects in course of crime investigation in the Kathmandu Valley since it was first introduced on February 6, 2014.

Lie detector has been used in 35 districts so far.

Polygraph test was conducted on 18 suspects of thefts, 17 murders, three rapes, two frauds, one disappearance and one bogus SLC examinee.

During interrogation, 19 persons made it through the test while 23 failed. Nine of the suspects were women. Those clearing the polygraph test are deemed innocent.

The law enforcement agency has 12 polygraph kits and 10 examiners certified by the American Polygraph Association.

The MPO, Central Investigation Bureau, Special Bureau, Narcotics Control Bureau and Eastern Regional Police Office, Biratnagar have been using lie detectors.

However, the Central Polygraph Section in the Crime Investigation Department also deputes examiners with necessary kits to any police unit on demand.

Polygraph system is also called ‘psycho-physiological detection of deception’ and it is one of the techniques of credibility assessment.

Polygraph technique has been found to be effective in making the suspects speak the truth during crime investigation, said Police Commissioner AIGP Pratap Singh Thapa.

Polygraph is being used for criminal and internal investigation guided by Nepal Police Polygraph Directive, 2014. Polygraph examinations are scientifically accepted as a tool in crime investigations.

The machine records changes in physiological characteristics, such as respiration, heartbeat and blood pressure. Four to six sensors are attached to a person during a polygraph test.

The sensors usually record the person’s breathing rate, pulse, blood pressure, perspiration and sometimes arm and leg movement.

A significant change in behaviour such as faster heart rate, higher blood pressure and increased perspiration indicate that the person is lying.

However, these test reports cannot be produced in court as evidence.