The Instigator
Con (against)
4 Points
The Contender
Pro (for)
0 Points

Lie Detectors are Effective and Beneficial

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Post Voting Period
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Voting Style: Open Point System: 7 Point
Started: 2/15/2014 Category: Society
Updated: 3 years ago Status: Post Voting Period
Viewed: 737 times Debate No: 46025
Debate Rounds (3)
Comments (2)
Votes (1)




Round 1: Stance
Round 2: Arguments/Rebuttal
Round 3: Rebuttal/Conclusion

Lie Detectors are terrible.
They are highly ineffective and harmful to all.


They ARE effective, as mine has just detected your statement as a lie.
Debate Round No. 1


I thank the Pro for accepting my challenge. I wonder how Pro detected any lies in my statements are my opinion and therefore cannot be considered a lie and a polygraph, a typical lie detector, functions by documenting many physiological factors such as respiration, perspiration, and heart rate.

Despite the popular belief, lie detectors are not effective at all.

Lie detector, also known as a polygraoh, does not directly detect lies. Rather, they measure physical responses that accompany emotions. The examier notes these responses as one answers questions. Examiners first start with a control question to establish base rates. The examiner determines the truth in the answers by analyzing the rise and fall of these physiological responses.

First of all, the lie detector operates under a false assumption that people remain calm when telling the truths. Its principles iunder which it operates are crude and false. Although lie detectors may look scientific and credible, they are not falseproof. According to the reseach conducted by the American Polygraph Association itself, polygraph was proven accurate only about 80% of time. [1] This means that 1 in 5 people tested by the lie detectors are falsely accused of crimes. Also, the polygraph accuracy rate at around 65 percent that is only slightly better than the 50 percent correct one would get by flipping a coin. [2] The rate of inaccuracy is too high for any judicial system to use the results of polygraph as solid evidence.

In addition, many of the questions asked evoke heightened tension and arousal. The questions may be intrusive or accusatory causing some people distressed. The fear of being disbelieved also contribute to the unreliability of polygraphs. When a mother in Yakima, Washington was accused of sexually abusing her step-son, she failed the polygraph test. Upon further investigation, she was asked disturbing and accusatory questions. The accused mother understandably reacted with greater perspiration and blood pressure when asked those types of questions. Fortunately, the mother's attorney located a scientific expert who persuaded the jury that polygraph is not a credible evidence of guilt. [3] As such there are countless instances of polygraph tests that considered innocent people guilty.

Secondly, polygraph cannot distinguish among anxiety, irritation, and guilt. Studies by psychologiests David Lykken and Leonard Saxe indicate that people's physiological arousal is much the same for most emotions. They go on to state that a polygraph test err approximatel 33% of the time. They criticize that the 'lie detetcting test' actually measures the level of fear and anxiety. [4] It is a fact that polygraph cannnot distinguish guilt from honest fear.

I eagerly await Pro's arguments and rebuttals.

[3] Myers, David G.. Psychology. 7th ed. New York: Worth Publishers, 2004. Print.
[4] Vrij, Aldert. Detecting lies and deceit: pitfalls and opportunities. 2nd ed. Chichester: John Wiley, 2008. Print.


BGreeneID forfeited this round.
Debate Round No. 2


Since the Pro has forfeited his second round, I, unfortunately, have no arguments to rebut.

Pro has failed to provide any examples nor arguments to back his opinion up.

Lie detectors are ineffective and may be harmful.

It is too inaccurate for them to be used as a solid evidence in the judicial system.
Innocent people may be shown to be guilty and the guilty may be presented as innocent according to the polygraph.
It cannot distinguish between anxiety and guilt, both of which result in changes in perspiration rate, respiration rate and heart rate.

1 in 3 innocent people are shown to be guilty. 33% is an extremely high rate. You could be in that unfortunate 33%.

Vote Con!


BGreeneID forfeited this round.
Debate Round No. 3
2 comments have been posted on this debate. Showing 1 through 2 records.
Posted by sewook123 3 years ago
Well if you are saying polygraphs can measure your physiological factors accurately, I am with you.
However, that is not what this debate is about.
It's about how polygraphs or lie detectors are ineffective and may cause harm.
As I stated in my arguments, polygraphs are NOT 100% effective in distinguishing guilty from those who are simply suffering from anxiety.
Please read my arguments for more detailed answer.
Posted by Actionsspeak 3 years ago
Polygraphs simply measure you (tempature, heart rate etc.) and are 100% effective. Their are only errors when humans misread them.
1 votes has been placed for this debate.
Vote Placed by Krazzy_Player 3 years ago
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Total points awarded:40 
Reasons for voting decision: FF