Scratch a lie...

I watched the movie "Ray" last evening and when Ray Charles Robinson was a boy, his mother cautioned, "Scratch a lie, find a thief!"
Any ideas on origin? Is this a Southern/Negro saying or is it more widespread?
As ESC posted earlier they also referred to "Devil's Music."

The "devils music" was probably blues or jazz. Those genres were regarded much the same as Metal was in the 80's. I believe blues/jass was highly associated with heroine and opiate use.

as for the phrase, i've never heard it before either, it's a good one though, it's going in my repitoire