noun
lie detector
A device that measures physiological responses to determine if someone is lying.
警察は容疑者に嘘発見器を使った。
The police used a lie detector on the suspect.
Standard kanji spelling.
Mixed kana-kanji spelling, common in casual writing.
Katakana used for emphasis or informal style.
ポリグラフ is the technical term for a polygraph, while 嘘発見器 is the common Japanese word for a lie detector.
Compound of 嘘 (uso, 'lie') + 発見 (hakken, 'discovery') + 器 (ki, 'device').