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Psychology professor Aldert Vrij said some law enforcement agencies over-rely on machines to detect lies ("Busting the myths of lie detection"; last Sunday).
Our Sexual Assault Befrienders Service has encountered cases where those filing complaints of sexual assault or rape were required to take a polygraph lie detector test while making a police report.
Should this practice be allowed to continue, given international expert consensus on the poor accuracy and reliability of these tests?
In 2004, the British Psychological Society found that "even in the most favourable circumstances, polygraphic lie detection accuracy is not high".
In 2003, the United States National Research Council concluded that the polygraph's reliability was questionable, and neither technological nor methodological advancement was likely to improve it.
A polygraph does not directly detect deception. Instead, it measures physiological responses such as blood pressure and pulse rate, believed to result from psychological states accompanying deception.
These responses, however, can be caused by many other factors such as embarrassment, outrage or distress.
Administering the polygraph to rape and sexual assault complainants inevitably involves questioning them about highly sensitive and potentially distressing matters, which is likely to elicit emotional responses. This raises the possibility that the polygraph results become especially inaccurate.
Due to these concerns, many jurisdictions have discontinued the use of polygraph testing on rape and sexual assault complainants.
Polygraph results are not admissible in court in Singapore, and the process and reasons for administering the test are not generally made clear to the victims.
Many victims of sexual crimes do not make police reports because they fear being disbelieved. Forcing them to take a lie detector test reinforces their fear, and is of dubious value to the investigation.
Thus, we recommend that the practice be discontinued.
Sumedha Jalote (Ms)
Communications Executive
Association of Women for Action and Research
Our Sexual Assault Befrienders Service has encountered cases where those filing complaints of sexual assault or rape were required to take a polygraph lie detector test while making a police report.
Should this practice be allowed to continue, given international expert consensus on the poor accuracy and reliability of these tests?
In 2004, the British Psychological Society found that "even in the most favourable circumstances, polygraphic lie detection accuracy is not high".
In 2003, the United States National Research Council concluded that the polygraph's reliability was questionable, and neither technological nor methodological advancement was likely to improve it.
A polygraph does not directly detect deception. Instead, it measures physiological responses such as blood pressure and pulse rate, believed to result from psychological states accompanying deception.
These responses, however, can be caused by many other factors such as embarrassment, outrage or distress.
Administering the polygraph to rape and sexual assault complainants inevitably involves questioning them about highly sensitive and potentially distressing matters, which is likely to elicit emotional responses. This raises the possibility that the polygraph results become especially inaccurate.
Due to these concerns, many jurisdictions have discontinued the use of polygraph testing on rape and sexual assault complainants.
Polygraph results are not admissible in court in Singapore, and the process and reasons for administering the test are not generally made clear to the victims.
Many victims of sexual crimes do not make police reports because they fear being disbelieved. Forcing them to take a lie detector test reinforces their fear, and is of dubious value to the investigation.
Thus, we recommend that the practice be discontinued.
Sumedha Jalote (Ms)
Communications Executive
Association of Women for Action and Research
