It's not used to detect lies, it's used to measure how a person reacts under pressure. It's a low-level torture device meant to intimidate. The fact that polic

It's not used to detect lies, it's used to measure how a person reacts under pressure. It's a low-level torture device meant to intimidate. The fact that police services can use it to extract confessions is just a nice bonus, and it's really a really cheap alternative to conducting a complete and thorough investigation. Police policy has for a long time favored confessions over investigations.