from Wiktionary, Creative Commons Attribution/Share-Alike License
- a murderer will always be discovered.
- secrets or hidden crimes will eventually be exposed or discovered; nothing that is secret can remain a secret forever.
The phrase murder will out, literally "murder will become public", appears as far back as Geoffrey Chaucer's works. The phrase is often linked to the superstition that a murderer's presence near the corpse will be indicated by fresh bleeding. (Wiktionary)