- Movie: Proof of Innocence (English title) / Special Investigation: Condemned Criminal’s Letter (literal title)
- Revised romanization: Teukbyeolsusa: Sahyoungsuui Pyeonji
- Hangul: 특별수사: 사형수의 편지
- Director: Kwon Jong-Kwan
- Writer: Kwon Jong-Kwan
- Producer: Kim Jae-Yong
- Cinematographer: Yoo Uk, Kim Jung-Woo
- Release Date: June 16, 2016
- Runtime: 120 min.
- Genre: Crime / Drama
- Distributor: Next Entertainment World
- Language: Korean
- Country: South Korea
The manager (Kim Myung-Min) of an attorney’s office, who was once a detective, receives a letter from prison. The letter concerns a prisoner (Kim Sang-Ho) who insists he is innocent. The manager of the attorney’s office learns that the detective in charge of the prisoner’s case is a former rival of his. To gain personal revenge, he begins investigating the case.