noun
Legal term for a person held in custody, typically in a police station or detention facility.
被留置者の権利は法律で守られている。
The rights of detainees are protected by law.
Compound of 被 (hi, 'receiving') + 留置 (ryūchi, 'detention') + 者 (sha, 'person'). The exact historical derivation is uncertain, but the word follows standard legal terminology patterns.