A formal, somewhat dated term for a police officer. In modern Japanese, 警察官 (けいさつかん) is the standard word.
The title '警察吏員' is often seen in old documents.
The standard modern term for a police officer. 警察吏員 is a rarer, more formal equivalent.
Compound of 警察 (police) and 吏員 (official, clerk). The exact historical origin is uncertain, but it follows a pattern of formal bureaucratic titles.