8 ms·

I thought that polygraphs were not accepted as evidence in court, but are still used by some government and private agencies. Also, just curious, have they bee

I thought that polygraphs were not accepted as evidence in court, but are still used by some government and private agencies. Also, just curious, have they been discredited as in that double-blind trials show no more than a 50/50 chance of being correct (i.e., flipping a coin)? Or is it that a high enough percentage of people will fail them even if innocent, or pass them even if guilty? The thing I don't like about them is the method of reading them, where it is up to the subjective judgment of the examiner. That is, there isn't an algorithm that can be written down so that, for example, an untrained person or computer program can read it (and therefore be subjected to large enough random tests).

Retra 8y ago
What does it mean for a polygraph to be "correct?" They're not lie detectors, they are stress detectors. You can't "fail" a polygraph in any reliable sense.
chooseaname 8y ago
> I thought that polygraphs were not accepted as evidence in court... Only if you "pass". Fail one and admissible or not, it'll be brought up.
- deleted 8y ago
  [deleted]
- brianpgordon 8y ago
  I thought this smelled like totally useless Reddit-style cynical speculation, and 30 seconds of Googling confirmed my suspicion. No state allows admitting polygraph results without both parties' consent. Federal courts may or may not allow them depending on the judge, but if the judge allows them then the defendant is free to submit their passed polygraph (for whatever that's worth) just as equally as the prosecution is free to submit a failed one.
  - davvolun 8y ago
    That's my understanding as well. https://www.hg.org/legal-articles/is-a-polygraph-test-admissible-as-evidence-31737 https://www.hg.org/legal-articles/is-a-polygraph-test-admiss...
- pc86 8y ago
  > admissible or not, it'll be brought up That's not how it works, and even a public defender working 20 hour days who doesn't know their defendant's name would be able to get a mistrial.
  - chooseaname 8y ago
    In the stairwell outside the court room: "Look, I know your guy went for a polygraph, but you've not brought it up, so I assume he didn't do well. Here's what I can offer..."
disishhsha 8y ago
The polygraph test is an interrogation technique. The examiner uses the reading to guide the questioning. I think taking a human out of that loop would be as difficult as a Turing test.
zik 8y ago
> have they been discredited as in that double-blind trials show no more than a 50/50 chance of being correct? Yes. The reading of polygraphs is very subjective and it's been found that they reflect only whether the person administering the test thinks the subject is guilty.
- darkpuma 8y ago
  They also reflect whether or not the subject of the test believes the test works. In practice polygraphs are used as a form of psychological torture, used to frighten people into giving confessions. Of course whether a polygraph can frighten an innocent person enough to falsely confess is another matter, but if the subject is guilty and understands how polygraphs (don't) work, they can deceive the person administering the test very easily. There is no shortage of spies that have passed polygraphs regularly and reliably with flying colors.
  - wahern 8y ago
    Obligatory scene from The Wire: https://youtu.be/AJ5aIvjNgao?t=115 https://youtu.be/AJ5aIvjNgao?t=115
- auiya 8y ago
  You can read the National Academy of Sciences' conclusions on the polygraph and lie detection in their paper here - https://www.nap.edu/read/10420/chapter/10 https://www.nap.edu/read/10420/chapter/10
- samstave 8y ago
  I know this will sound stupid - but its a serious showerthought of a question: Are "clearers" from Scientology any 'better' at reading a polygraph than non-"clearers"
  - SEJeff 8y ago
    Auditors in scientology are in fact using a primitive polygraph device to get gullible people to divulge their deepest and darkest secrets. This is something the "church" has used to blackmail and discredit their enemies.
leggomylibro 8y ago
They're notoriously inaccurate, but I don't think that courts have given up on them yet. And if you think that's bad, just wait until you're given an inaccurate brain scan to tell whether you're lying. https://www.sciencedirect.com/science/article/pii/S0169260708002484 https://www.sciencedirect.com/science/article/pii/S016926070... >The rates of correct detection in guilty and innocent subjects were 86%, which was better than other previously used methods. Eh, that sounds close enough to 'beyond a reasonable doubt', right?
- daxorid 8y ago
  Eyewitness testimony is also extraordinarily inaccurate, but courts overwhelmingly consider it as strong evidence of guilt. https://www.scientificamerican.com/article/do-the-eyes-have-it/ https://www.scientificamerican.com/article/do-the-eyes-have-...
- jdironman 8y ago
  People win the lottery every day and those odds are very much against thrm, but they play the odds in hopes of a positive outcome. When talking about life and liberty and negative consequences there should be as few chances taken as possible. I don't think 86% is the best we can do.
6nf 8y ago
Individuals can also 'train' for polygraphs, basically learning to spoof the readings. So really you just can't rely on polygraphs for anything at all.
- posterboy 8y ago
  People can also simply lie, but statements are still considered testimony.
  - 6nf 8y ago
    Yea the polygraph adds nothing useful here
- general8bitso 8y ago
  Clench your anus, a la ‘The Americans’ tv series.

Retra 8y ago

What does it mean for a polygraph to be "correct?" They're not lie detectors, they are stress detectors. You can't "fail" a polygraph in any reliable sense.

chooseaname 8y ago

> I thought that polygraphs were not accepted as evidence in court... Only if you "pass". Fail one and admissible or not, it'll be brought up.

deleted 8y ago
[deleted]
brianpgordon 8y ago
I thought this smelled like totally useless Reddit-style cynical speculation, and 30 seconds of Googling confirmed my suspicion. No state allows admitting polygraph results without both parties' consent. Federal courts may or may not allow them depending on the judge, but if the judge allows them then the defendant is free to submit their passed polygraph (for whatever that's worth) just as equally as the prosecution is free to submit a failed one.
- davvolun 8y ago
  That's my understanding as well. https://www.hg.org/legal-articles/is-a-polygraph-test-admissible-as-evidence-31737 https://www.hg.org/legal-articles/is-a-polygraph-test-admiss...
pc86 8y ago
> admissible or not, it'll be brought up That's not how it works, and even a public defender working 20 hour days who doesn't know their defendant's name would be able to get a mistrial.
- chooseaname 8y ago
  In the stairwell outside the court room: "Look, I know your guy went for a polygraph, but you've not brought it up, so I assume he didn't do well. Here's what I can offer..."

disishhsha 8y ago

The polygraph test is an interrogation technique. The examiner uses the reading to guide the questioning. I think taking a human out of that loop would be as difficult as a Turing test.

zik 8y ago

> have they been discredited as in that double-blind trials show no more than a 50/50 chance of being correct? Yes. The reading of polygraphs is very subjective and it's been found that they reflect only whether the person administering the test thinks the subject is guilty.

darkpuma 8y ago
They also reflect whether or not the subject of the test believes the test works. In practice polygraphs are used as a form of psychological torture, used to frighten people into giving confessions. Of course whether a polygraph can frighten an innocent person enough to falsely confess is another matter, but if the subject is guilty and understands how polygraphs (don't) work, they can deceive the person administering the test very easily. There is no shortage of spies that have passed polygraphs regularly and reliably with flying colors.
- wahern 8y ago
  Obligatory scene from The Wire: https://youtu.be/AJ5aIvjNgao?t=115 https://youtu.be/AJ5aIvjNgao?t=115
auiya 8y ago
You can read the National Academy of Sciences' conclusions on the polygraph and lie detection in their paper here - https://www.nap.edu/read/10420/chapter/10 https://www.nap.edu/read/10420/chapter/10
samstave 8y ago
I know this will sound stupid - but its a serious showerthought of a question: Are "clearers" from Scientology any 'better' at reading a polygraph than non-"clearers"
- SEJeff 8y ago
  Auditors in scientology are in fact using a primitive polygraph device to get gullible people to divulge their deepest and darkest secrets. This is something the "church" has used to blackmail and discredit their enemies.

leggomylibro 8y ago

They're notoriously inaccurate, but I don't think that courts have given up on them yet. And if you think that's bad, just wait until you're given an inaccurate brain scan to tell whether you're lying. https://www.sciencedirect.com/science/article/pii/S0169260708002484 https://www.sciencedirect.com/science/article/pii/S016926070... >The rates of correct detection in guilty and innocent subjects were 86%, which was better than other previously used methods. Eh, that sounds close enough to 'beyond a reasonable doubt', right?

daxorid 8y ago
Eyewitness testimony is also extraordinarily inaccurate, but courts overwhelmingly consider it as strong evidence of guilt. https://www.scientificamerican.com/article/do-the-eyes-have-it/ https://www.scientificamerican.com/article/do-the-eyes-have-...
jdironman 8y ago
People win the lottery every day and those odds are very much against thrm, but they play the odds in hopes of a positive outcome. When talking about life and liberty and negative consequences there should be as few chances taken as possible. I don't think 86% is the best we can do.

6nf 8y ago

Individuals can also 'train' for polygraphs, basically learning to spoof the readings. So really you just can't rely on polygraphs for anything at all.

posterboy 8y ago
People can also simply lie, but statements are still considered testimony.
- 6nf 8y ago
  Yea the polygraph adds nothing useful here
general8bitso 8y ago
Clench your anus, a la ‘The Americans’ tv series.