The following expressions are idiomatic:
1) "I wouldn't touch Z with a 10-foot pole", meaning the speaker wouldn't want to be involved with Z in any way.
2) "S couldn't find his way out of a paper bag," meaning S has a bad sense of direction.
Is there an idiomatic hyperbole of the same form which means "I wouldn't trust Z at all"?
Edit: to be more precise, I'm looking for something where the image/hyperbole is related to being untrustworthy.