It's not voodoo, please stop spreading FUD. The name -- lie detector -- is complete horseshit because it doesn't detect lies, but that doesn't detract from its effectiveness as a low-level torture device.

The physiological measurements may be inadmissible to the courts, but if you happen to confess to a crime during the (thoroughly unpleasant) interrogation then that is perfectly admissible. This key point here is why LEOs are so adamant about subjecting their prisoners to polygraph examinations.

Over 95% of Federal court cases end as a result of a plea bargain, despite the plea bargain being offered under threat of lifetime imprisonment and death.