innocent as a lamb

(as) innocent as a lamb

1. Blameless or faultless. I swear, I didn't pull the fire alarm—I'm innocent as a lamb!
2. Unsophisticated, inexperienced, or gullible. This is her first job—she's as innocent as a lamb.
See also: innocent, lamb
Farlex Dictionary of Idioms.

*innocent as a lamb

 and *innocent as a newborn babe 
1. guiltless. (*Also: as ~.) "Hey! You can't throw me in jail," cried the robber. "I'm innocent as a lamb."
2. naive; inexperienced. (*Also: as ~.) She's eighteen years old, but innocent as a newborn babe.
See also: innocent, lamb
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • (as) innocent as a lamb
  • innocent
  • newborn
  • (as) innocent as a newborn babe
  • babe
  • fall off the cabbage truck
  • fall off the turnip truck
  • turnip
  • just fell off the turnip truck
  • greenhorn