noun
written statement; affidavit; deposition
A formal written record of testimony, typically used in legal or investigative contexts.
警察は容疑者から供述書を取った。
The police took a written statement from the suspect.
裁判で供述書が証拠として提出
The deposition was submitted as evidence in court.
陳述書 is a broader term for any written statement, not necessarily under oath or in a criminal context.
Compound of 供述 (testimony) + 書 (document). The exact historical derivation is uncertain, but the components are transparent.