I think they are crap
No, its just they can be faked so easily with controlled breathing and blood pressure..
Yes, I have taken both. A simple benzo or even cyclobenzaprine will throw them off.
They are inaccurate because they really reflect guilt, nervousness or anxiety rather than lying. <br />
Someone can be telling the truth but be nervous about answering & it will register as a "blip" against them. Someone else might be able to lie while being able to breathe normally & maintain normal heart rate because they have no guilt or anxiety about lying or because they have trained themselves to control their reactions & it will not register against them.<br />
Most law enforcement agencies don't use them to place innocent civilians in jail, as they can place people in jail without using them. Most courts won't accept them as evidence either. Law enforcement agencies may use them to get an idea who might be lying, as most people have enough of a conscience to be anxious when they are lying.
They are not accurate at all. But the idea they are, makes them powerful
There can tell deception and stress, but not necessarily deception on what.
Not that accurate. Nor are the voice stress tests.
They may be accurate if the person doesn't cheat. But they can easily be beaten. I've done it twice - it wasn't for something I did either time, it was protecting friends. All you have to do is have one mixed drink about a half hour to an hour before time. The alcohol relaxes you just right that you pass. :)
I could never lie to you...