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< Back to question Should polygraphs be admissible in court? Show more Show less

Once called "the strip searches of the mind", polygraph test creators maintain that their lie detectors can detect when a suspect is lying in 80-95% of cases. Should we use them in the justice system to secure convictions? Or are polygraphs a dangerous and gross violation of a suspect's legal rights?

No, lie detectors should not be admissible in court Show more Show less

Polygraphs are not accurate enough to be used in legal proceedings.
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Polygraphs violate the right to not self-incriminate

Defendants have the right not to self-incriminate. Lie detectors would infringe on that right.
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Introducing lie-detector tests into court proceedings would represent a clear violation of a suspects right to not self-incriminate.

The Argument

A suspect always has the right to remain silent and not answer a question if the answer they provide could self-incriminate. If the suspect is forced to carry out a lie-detector test, the answers they give to the questions asked could potentially self-incriminate. Similarly, if a polygraph test was introduced as a voluntary component in legal proceedings, if a suspect refused to take one and the refusal was presented to a jury as evidence, it could affect their decision, eliminating the presumption of innocence until proven guilty. However polygraphs were to be used, they would compromise the basic principles of a legal trial.

Counter arguments

Polygraph questions that do not deal with the specifics, including where/when the crime took place, who the victim was and the names of other people involved, would not be sufficiently detailed to violate a defendant’s right not to self-incriminate. The burden of proof would still be on the prosecutor to incriminate the defendant and prove beyond reasonable doubt that they committed the crime in question. [1] The polygraph would not provide a lead or link to evidence used in the conviction. However, it would be useful to background information and used to show the defendant’s character in front of a jury. Also, the term "self-incrimination" does not really apply here. The safeguards designed to protect against self-incrimination were supposed to prevent the government from forcing defendants to testify against themselves. They were not designed to prevent law enforcement officers from extracting information from them. Consider a case where someone gets arrested for drink driving. They go to the police station, where the police take their blood. Blood tests reveal that the driver was driving intoxicated. Would this person be able to argue that their right to self-incrimination was infringed because law enforcement used evidence taken from the defendant in their case? No. Lie detector tests function in the same way. They do not violate a defendant's right to not self-incriminate because the state will not get to the defendant to testify. It is simply a mechanism to extract evidence from the suspect, in much the same way as a blood test does.


[P1] Polygraphs violate a defendant's right not to self-incriminate. [P2] Therefore, they should not be admissible in court.

Rejecting the premises

[Rejecting P1] Polygraphs no more violate an individual's right to not self-incriminate than a blood test or breathalyser reading. [Rejecting P2] They do not violate the design of the Fifth Amendment. Therefore, they should be admissible in court.



This page was last edited on Monday, 20 Apr 2020 at 07:28 UTC

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