Lie detectors are able to measure physical changes that occur in most people
when a lie is being told. Because the truth does not change with time, a lie remains a lie.
A very small percentage of the population---primarily, those with antisocial tendencies (not in the sense we usually think of "antisocial," as in, "doesn't like parties," or "doesn't have lots of friends," but antisocial traits as defined by the criteria for defining antisocial personality disorder; the traits can be present without the person reaching the magnitude of being a sociopath), or strong NPD tendencies, are able to
"fool" the polygraph.
In the hands of a VERY skilled polygrapher, however, questions are rephrased in various ways so that deception is revealed. (This is also how psychiatrists are able to diagnose the disorders; the questions on the tests are rephrased a number of different ways----and differences among responses are significant.)
ANYWAY---though it is a flawed tool, it is a good tool, more often than not giving useful information.
Questions have to be carefully chosen. The polygrapher must be skilled.
If she does not remember an answer, it will not affect the results. If she says she does not remember (but really does), deception will be shown.
As for hypnosis, there's a REAL issue when it comes to getting to the truth: if the person under hypnosis WANTS the truth revealed, because, for example, s/he genuinely cannot remember and wants to know---then, yes---you may get answers.
HOWEVER---and this is very important---if a hypnotic subject does not want to reveal or do something, hypnosis will not elicit anything for which s/he has any resistance.
It's simply NOT a good method for eliciting information your wife is unwilling to give up.
I disagree with Fightingmad--18 months is not very far in (though it seems like an eternity). Rather, I disagree with his wording---that at 18 months you "feel the need" to do this.
That you do not feel confident in your wife's answers is a reflection of HER failure to bolster confidence.
At 18 months, this is not unusual.
Emptyshelldad, your profile says volumes about your pain--but says very little about what happened. Did you stumble across your wife's infidelity? How did she respond when you found out? Was NC established? (Are you sure it has been established?) You say you've asked her a slew of questions---how does she respond? Does she answer them without anger or blameshifting? Are the answers consistent? Does she show remorse, or is she just ticked she got caught?
Has she gone to IC? Have you? Are the two of you ready for MC? (If she's not really remorseful, it's not emotionally safe for the BS to go into MC, IMO.)
I guess my thoughts boil down to this: If you are not getting what you need at 18 months, it's time to examine the situation. Will answers from a polygraph give you what you need? Or do you need something MORE than the truth---like remorse, a feeling that you are safe in your marriage, etc.?
I never got answers from my husband. I never will--and because of this, I ended our marriage.
That said, the answers were only a very small portion of what I needed. Had he been remorseful, intent on repairing our marriage with me, and so on---I might have been willing to accept his glacial pace of response.
As it was, it wasn't just answers he never intended to give me.
What is your wife giving you to work with?