Can the defense offer character evidence on a witness for any purpose other than truthfulness? R. 608 seems to say no. There is a lot of caselaw about a DEFENDANT's character for truthfulness or being law abiding.

Basically, can they attack my witnesses (other than convictions) for truancy and various school disturbances or minor law violations?

Sorry, I've been trying to research this today and my brain is fried.

One more question, can an opinion (not reputation) witness testify on the basis of one incident with the actor? i.e. An officer has been specifically lied to by a potential defense witness in the past. Can his opinion be based on that and what is the predicate?

As to your basis-for-an-opinion question, Judge Cochran says: "Such problems are solved by a proper administration of Rules 403, 405, and 701." Cochran, Texas Rules of Evidence Handbook at 596 (5th ed. 2003). She cites United States v. Dotson, 799 F.2d 189, 190-93 (5th Cir. 1986).