A polygraph, also known as a lie detector is a machine that law enforcement authorities around the world, including Singapore, use while investigating crimes. If you have been asked to take one, immediately contact a criminal lawyer to get further legal advice.

The polygraph measures certain physiological responses such as breathing patterns, pulse and skin conductivity and blood pressure via various attachments to your chest and a single hand. The polygrapher will then ask a series of questions, some relevant to the case and the machine will then look out for irregularities in your reactions when answering these questions.

However, due to the simple reason that there are no specific physiological reactions that can be associated with lying, polygraph tests can be unreliable and thus, inadmissible as evidence against an accused person in a criminal case.

When is a Polygraph Test Used?

Law enforcement agencies generally use polygraph tests when they are undecided, or lack enough evidence to recommend someone for prosecution. If the Police for example, are unsure of a suspect’s guilt, a failed polygraph test might sway them towards recommending further investigation, or prosecution. A passed polygraph test might be enough to convince the police to stop continuing the investigation if there are no other further evidence of a person’s guilt.

Must You Attend a Polygraph Test?

Although the results of a polygraph test are inadmissible as evidence in a criminal case, how you react to the police’s invitation might also affect their assessment of your conduct.

For example, if you decide to accept the invitation and take the test, a pass result will most likely clear you and if you fail the test, the police may recommend prosecution.

However, if you decline the invitation, the police may conclude that you might be guilty and recommend prosecution. They may also record another statement with your reasons for choosing to decline the test. You may answer that your only reason for declining was based on legal advice you received which is protected by solicitor-client privilege, making it harder for the police to ask you further related questions.

Mr Amarjit Singh Sidhu of Amarjit Sidhu Law Practice has represented numerous clients in a wide variety of matters over the years from traffic offences, family disputes to high-profile criminal cases and will be able to provide you with timely advice on your case. With a vast knowledge of Singapore’s laws and a wealth of experience, Mr Amarjit Singh Sidhu will be able to provide valuable and timely advice for your situation. For more information, feel free to contact us for a consultation.


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