Green’s Dictionary of Slang

innocent n.

1. (US) a corpse.

[US]Matsell Vocabulum.

2. (Aus./US Und.) a prisoner [since the prisoner is locked up they cannot be accused of any subsequent crimes until release; Irwin suggests the near universal claim by criminals that they are innocent].

[US]Matsell Vocabulum 44: innocents Convicts, because it is supposed that they cannot commit a crime.
[Aus]Crowe Aus. Sl. Dict. 38: Innocents, persons in gaol.
[US] ‘Jargon of the Und.’ in DN V 451: Innocent, A convict.
[US]Irwin Amer. Tramp and Und. Sl. 107: Innocent. – A convict or other prisoner.

3. (UK Und.) a sentence passed on an innocent man.

[UK]Daily Tel. 16 Oct. in Ware (1909) 157/2: An ex-convict, who admitted having undergone long terms of penal servitude, applied to Mr Denman, at Westminster, complaining that his worship gave him three months’ ‘innocent’ in May 1893 at South-Western Police Court.

4. (US black) an ironic ref. to white liberals wishing to become involved in the black struggle [from stock liberal disavowals of racism, prejudice, the responsibility for slavery etc.].

[US]Wentworth & Flexner DAS.