# Would an infallible lie detector be a boon or a curse for humanity? **URL:** \ **Category:** Great Debates\ **Created:** [December 21, 2014, 4:30am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801 "2014-12-21T04:30:18Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Gozu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gozu/32/6615_2.png) [@Gozu](https://boards.straightdope.com/u/Gozu)\ **Post date:** [December 21, 2014, 4:30am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/1 "2014-12-21T04:30:18Z")
I was listening to Serial and how it would be so easy to know if someone is guilty or innocent if we had a real lie detector. I’m wondering if this, and other benefits outweigh the drawbacks, especially if it fell in the wrong hands. What say you? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [December 21, 2014, 4:35am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/2 "2014-12-21T04:35:42Z")
It’s going to depend on how portable it is and how widespread. Will it be the size of a marker and available in every store or the size of a cargo van and confined to the legal system? ---
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [December 21, 2014, 4:44am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/3 "2014-12-21T04:44:22Z")
Well, torture\* would become completely effective. More efficient, too, depending on how creative you are or how sensitive the machine is… “Does the courier’s name start with the letter ‘A’? If ‘yes,’ scream.” _Taser_ _Shriek_ _Machine dings_ “Alrighty then! Does the NEXT letter of the courier’s name start with ‘A’?” _Taser_ _Shriek_ _Machine buzzes_ “Got it…does the next letter of the courier’s name start with ‘B’?” _Taser_ _Shriek_ _Machine dings_ “Now we’re getting somewhere! Alright, does the third letter of the courier’s name start with ‘A’…?” [Etc] (I’m kidding, of course; you could probably do the above scenario without shocking someone’s eyeballs. But it’s not as funny.) \*Well, torture-for-interrogation, that is. Torture for punishment or intimidation is really a different field. ---
**Author:** ![Count\_Dracula](https://avatars.discourse-cdn.com/v4/letter/c/54ee81/32.png) [@Count\_Dracula](https://boards.straightdope.com/u/Count_Dracula)\ **Post date:** [December 21, 2014, 4:44am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/4 "2014-12-21T04:44:38Z")
It would certainly put all of the politicians out of business. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [December 21, 2014, 4:52am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/5 "2014-12-21T04:52:39Z")
How would it react to “This statement is a lie”? ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [December 21, 2014, 4:55am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/6 "2014-12-21T04:55:10Z")
It would lead to some very intricate compartmentalization of secret data. You can’t tell what you don’t know. Encryption would become vastly more vital than it is today. There’d be a lot more use of sealed orders. Also deceit and provocation. It would become a vital tactic to “allow” someone to get loose with information he thinks is true. It wouldn’t change the game all that much. We’re clever bastards; we’d find ways to maintain deception and secrecy. It might lead to more use of suicide pills if high-ranking personnel are in danger of capture. But, again, if a guy is carrying secret orders, and he disposes of them (old-time Naval couriers kept dispatches in lead-lined books, so they could be sunk) then what can he possibly tell? Meanwhile, for purposes of ordinary civil cases, it would be a huge boon, and would also be useful for many criminal trials. It would give a huge benefit to the defense position of “not guilty by reason of actual innocence.” If you could prove your innocence, the D.A. isn’t likely to waste his time pressing charges. It would eliminate the old gridlock of “it’s my word versus his.” I’m voting it would be a small boon for human civilization. ---
**Author:** ![Gozu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gozu/32/6615_2.png) [@Gozu](https://boards.straightdope.com/u/Gozu)\ **Post date:** [December 21, 2014, 5:10am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/7 "2014-12-21T05:10:32Z")
> [@running\_coach](#): > > It’s going to depend on how portable it is and how widespread. Will it be the size of a marker and available in every store or the size of a cargo van and confined to the legal system? The first one. ---
**Author:** ![Gozu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gozu/32/6615_2.png) [@Gozu](https://boards.straightdope.com/u/Gozu)\ **Post date:** [December 21, 2014, 5:11am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/8 "2014-12-21T05:11:59Z")
> [@ultrafilter](#): > > How would it react to “This statement is a lie”? It would mark it as truthful. Either that or it would violently explode, killing or injuring dozens around it. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [December 21, 2014, 5:15am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/9 "2014-12-21T05:15:30Z")
> [@Gozu](#): > > The first one. The end of civilization. We can’t handle the truth. 😃 ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [December 21, 2014, 5:30am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/10 "2014-12-21T05:30:53Z")
It would have interesting effects on authoritarian regimes. The ones that depend on fear to stay in power would be faced with a quandary; what do you do when you use this super lie detector to detect who is loyal - and the answer is “virtually no one”? On the other hand those that are more successful at creating true believers in the regime/its ideology will be able to find genuinely loyal people fairly easily - and they’ll risk collapsing _because_ they’ve filled all positions of authority with inflexible, irrational true believers. > [@Ranchoth](#): > > Well, torture\* would become completely effective. Not really, since torture is known to cause memory loss and the creation of false memories. And torture becoming a common practice would encourage people to suicide rather than surrender, and you can’t interrogate a corpse. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [December 21, 2014, 5:58am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/11 "2014-12-21T05:58:24Z")
It’s not a lie, if _you_ believe it. ---
**Author:** ![Critical1](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@Critical1](https://boards.straightdope.com/u/Critical1)\ **Post date:** [December 21, 2014, 6:20am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/12 "2014-12-21T06:20:54Z")
You would have to change some laws, before you get to ask me a single question as a suspect my lawyer is going to use it on the police, the detectives, and the prosecutor to make sure they actually have a valid reason for asking me any questions at all…not to mention that whole 5th amendment thing. and Politicians, omfg the end of both parties would be immediate. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [December 21, 2014, 6:33am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/13 "2014-12-21T06:33:16Z")
Disaster. Human survival is based on the lies we tell ourselves and others. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [December 21, 2014, 6:34am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/14 "2014-12-21T06:34:25Z")
Heck, if someone asks “Where were you on the night of the 24th?” and your reply is “none of your business”, would that register as true if you believe that the answer is none of their business? ---
**Author:** ![lel](https://avatars.discourse-cdn.com/v4/letter/l/8797f3/32.png) [@lel](https://boards.straightdope.com/u/lel)\ **Post date:** [December 21, 2014, 7:07am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/15 "2014-12-21T07:07:17Z")
> [@Bryan\_Ekers](#): > > It’s not a lie, if _you_ believe it. It would be amusing to see what happened when two people were marked as telling the truth on two statements that are wholly contradictory. Honestly, would this thing even have any effect given how adept people are at believing that things that are wrong are actually right and how notoriously poor people are at being eyewitnesses? ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [December 21, 2014, 7:51am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/16 "2014-12-21T07:51:27Z")
We may be close to this. Although for the near future it would probably be a large machine and therefore could have laws controlling it’s use. It could have dramatic affects on our justice system. > **[Can fMRI Really Tell If You're Lying?](https://www.scientificamerican.com/article/new-lie-detector/)** > > Will brain scans ever be able to tell if you're really being deceptive? [http://www.noliemri.com/](http://www.noliemri.com/) ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [December 21, 2014, 7:58am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/17 "2014-12-21T07:58:21Z")
> [@lel](#): > > It would be amusing to see what happened when two people were marked as telling the truth on two statements that are wholly contradictory. > > Honestly, would this thing even have any effect given how adept people are at believing that things that are wrong are actually right and how notoriously poor people are at being eyewitnesses? Exactly. Plenty of people think they have seen ghosts and alien spaceships; they aren’t lying, so a lie detector would mark them down as telling the truth. Does that mean ghosts and alien spaceships are real? ---
**Author:** ![Leaper](https://avatars.discourse-cdn.com/v4/letter/l/4bbf92/32.png) [@Leaper](https://boards.straightdope.com/u/Leaper)\ **Post date:** [December 21, 2014, 10:57am UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/18 "2014-12-21T10:57:03Z")
The trouble is that so many statements “X” are actually “I believe X”, with the first two words elided. And, of course, since a lie detecting machine cannot judge objective reality outside of the person it’s examining… ---
**Author:** ![The\_Other\_Waldo\_Pepper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_other_waldo_pepper/32/12370_2.png) [@The\_Other\_Waldo\_Pepper](https://boards.straightdope.com/u/The_Other_Waldo_Pepper)\ **Post date:** [December 21, 2014, 12:19pm UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/19 "2014-12-21T12:19:37Z")
> [@Bryan\_Ekers](#): > > Heck, if someone asks “Where were you on the night of the 24th?” and your reply is “none of your business”, would that register as true This message brought to you by The Other Waldo Pepper, who owns a restaurant called _None Of Your Business_; it’s next to _I Was At Home All Evening Reading A Good Book_. ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [December 21, 2014, 1:14pm UTC](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801/20 "2014-12-21T13:14:18Z")
Obviously people can refuse to answer (“none of your business”, is the equivalent of this), and obviously it’s only going to show what the person _believes_ to be true, but neither of those things mean that it would have no impact. An innocent person who’s been arrested for murder could quickly prove their innocence, for example. Sure, it would only show that they believe themselves to be innoncent, and I suppose that a prosecutor could try to argue that they could have alzheimers or something, but if I was on a jury it would take a lot to convince me that the defendant’s memory is that faulty. I have to wonder if it could ever be totally infallible. Imagine that such devices eventually became small, inexpensive, and easy to use. Maybe it lights up either red or green for a lie or the truth. Could a person use it on themselves to train themselves to lie without triggering the red light? [Next page](https://boards.straightdope.com/t/would-an-infallible-lie-detector-be-a-boon-or-a-curse-for-humanity/707801.md?page=2)